9 files changed, 487 insertions, 482 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 42d2502..498adc8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@ set(CMAKE_C_EXTENSIONS Off)
 # isogfx
 
 add_library(isogfx
+  src/asset.c
   src/isogfx.c)
 
 target_include_directories(isogfx PUBLIC
@@ -16,8 +17,7 @@ target_include_directories(isogfx PUBLIC
 
 target_link_libraries(isogfx PUBLIC
   filesystem
-  mem
-  mempool)
+  memstack)
 
 target_compile_options(isogfx PRIVATE -Wall -Wextra -Wpedantic)
 
diff --git a/demos/checkerboard/checkerboard.c b/demos/checkerboard/checkerboard.c
index 9d1791e..b408fc2 100644
--- a/demos/checkerboard/checkerboard.c
+++ b/demos/checkerboard/checkerboard.c
@@ -20,6 +20,9 @@ static const int TILE_HEIGHT  = TILE_WIDTH / 2;
 static const int WORLD_WIDTH  = 20;
 static const int WORLD_HEIGHT = 20;
 
+#define MEMORY_SIZE (2 * 1024 * 1024)
+uint8_t MEMORY[MEMORY_SIZE];
+
 static const TileDesc tile_set[] = {
     {.type   = TileFromColour,
      .width  = TILE_WIDTH,
@@ -35,6 +38,8 @@ static const TileDesc tile_set[] = {
      .colour = (Pixel){.r = 0xdc, .g = 0x76, .b = 0x84, .a = 0xff}},
 };
 
+#define NUM_TILES (sizeof(tile_set) / sizeof(tile_set[0]))
+
 typedef enum Colour {
   Black,
   White,
@@ -67,28 +72,28 @@ static bool init(GfxAppState* state, int argc, const char** argv) {
   (void)argc;
   (void)argv;
 
-  if (!(state->iso = isogfx_new(&(IsoGfxDesc){
-            .screen_width = SCREEN_WIDTH, .screen_height = SCREEN_HEIGHT}))) {
+  if (!((state->iso =
+             isogfx_new(&(IsoGfxDesc){.memory        = MEMORY,
+                                      .memory_size   = MEMORY_SIZE,
+                                      .screen_width  = SCREEN_WIDTH,
+                                      .screen_height = SCREEN_HEIGHT})))) {
     return false;
   }
   IsoGfx* iso = state->iso;
 
-  isogfx_resize(iso, SCREEN_WIDTH, SCREEN_HEIGHT);
-
-  if (!isogfx_make_world(
-          iso, &(WorldDesc){.tile_width   = TILE_WIDTH,
-                            .tile_height  = TILE_HEIGHT,
-                            .world_width  = WORLD_WIDTH,
-                            .world_height = WORLD_HEIGHT})) {
-    return false;
-  }
+  isogfx_make_world(
+      iso, &(WorldDesc){.tile_width   = TILE_WIDTH,
+                        .tile_height  = TILE_HEIGHT,
+                        .world_width  = WORLD_WIDTH,
+                        .world_height = WORLD_HEIGHT,
+                        .num_tiles    = NUM_TILES});
 
   const Tile black = isogfx_make_tile(iso, &tile_set[Black]);
   const Tile white = isogfx_make_tile(iso, &tile_set[White]);
   state->red       = isogfx_make_tile(iso, &tile_set[Red]);
   make_checkerboard(iso, black, white);
 
-  if (!(state->backend = iso_backend_init(iso))) {
+  if (!((state->backend = iso_backend_init(iso)))) {
     return false;
   }
 
diff --git a/demos/isomap/isomap.c b/demos/isomap/isomap.c
index b328bfa..efae7fd 100644
--- a/demos/isomap/isomap.c
+++ b/demos/isomap/isomap.c
@@ -5,6 +5,7 @@
 
 #include <assert.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 static const int WINDOW_WIDTH  = 1408;
 static const int WINDOW_HEIGHT = 960;
@@ -14,6 +15,9 @@ static const int MAX_FPS       = 60;
 static const int SCREEN_WIDTH  = 704;
 static const int SCREEN_HEIGHT = 480;
 
+#define MEMORY_SIZE (2 * 1024 * 1024)
+uint8_t MEMORY[MEMORY_SIZE];
+
 typedef struct GfxAppState {
   IsoBackend* backend;
   IsoGfx*     iso;
@@ -28,30 +32,30 @@ static bool init(GfxAppState* state, int argc, const char** argv) {
   (void)argc;
   (void)argv;
 
-  if (!(state->iso = isogfx_new(&(IsoGfxDesc){
-            .screen_width = SCREEN_WIDTH, .screen_height = SCREEN_HEIGHT}))) {
+  if (!((state->iso =
+             isogfx_new(&(IsoGfxDesc){.memory        = MEMORY,
+                                      .memory_size   = MEMORY_SIZE,
+                                      .screen_width  = SCREEN_WIDTH,
+                                      .screen_height = SCREEN_HEIGHT})))) {
     return false;
   }
   IsoGfx* iso = state->iso;
 
-  isogfx_resize(iso, SCREEN_WIDTH, SCREEN_HEIGHT);
-
   if (!isogfx_load_world(iso, "/home/jeanne/Nextcloud/assets/maps/demo-1.tm")) {
     return false;
   }
 
-  if (!isogfx_load_sprite_sheet(
-          iso,
-          "/home/jeanne/Nextcloud/assets/tilesets/scrabling/critters/stag/"
-          "stag.ss",
-          &state->stag_sheet)) {
+  if (!((state->stag_sheet = isogfx_load_sprite_sheet(
+             iso,
+             "/home/jeanne/Nextcloud/assets/tilesets/scrabling/critters/stag/"
+             "stag.ss")))) {
     return false;
   }
 
   state->stag = isogfx_make_sprite(iso, state->stag_sheet);
   isogfx_set_sprite_position(iso, state->stag, 5, 4);
 
-  if (!(state->backend = iso_backend_init(iso))) {
+  if (!((state->backend = iso_backend_init(iso)))) {
     return false;
   }
 
diff --git a/include/isogfx/asset.h b/include/isogfx/asset.h
index 298c469..9aeb55d 100644
--- a/include/isogfx/asset.h
+++ b/include/isogfx/asset.h
@@ -7,6 +7,8 @@
  */
 #pragma once
 
+#include <isogfx/types.h>
+
 #include <assert.h>
 #include <stdint.h>
 
@@ -18,16 +20,16 @@
 // -----------------------------------------------------------------------------
 
 typedef struct Ts_Tile {
-  uint16_t width;     // Tile width in pixels.
-  uint16_t height;    // Tile height in pixels.
-  Pixel    pixels[1]; // Count: width * height.
+  uint16_t width;  // Tile width in pixels.
+  uint16_t height; // Tile height in pixels.
+  uint32_t pixels; // Byte offset into the Ts_TileSet's 'pixels'.
 } Ts_Tile;
 
 typedef struct Ts_TileSet {
   uint16_t num_tiles;
-  uint16_t max_tile_width;  // Maximum tile width in pixels.
-  uint16_t max_tile_height; // Maximum tile height in pixels.
-  Ts_Tile  tiles[1];        // Count: num_tiles.
+  uint16_t _pad;
+  Ts_Tile  tiles[1]; // Count: num_tiles.
+  Pixel    pixels[]; // Count: sum_i(tile[i].width * tile[i].height).
 } Ts_TileSet;
 
 // -----------------------------------------------------------------------------
@@ -35,19 +37,17 @@ typedef struct Ts_TileSet {
 // -----------------------------------------------------------------------------
 
 typedef struct Tm_Layer {
-  union {
-    char tileset_path[ISOGFX_MAX_PATH_LENGTH]; // Relative to the Tm_Map file.
-  };
   Tile tiles[1]; // Count: world_width * world_height.
 } Tm_Layer;
 
 typedef struct Tm_Map {
+  char     tileset_path[ISOGFX_MAX_PATH_LENGTH]; // Relative to the Tm_Map file.
   uint16_t world_width;  // World width in number of tiles.
   uint16_t world_height; // World height in number of tiles.
   uint16_t base_tile_width;
   uint16_t base_tile_height;
   uint16_t num_layers;
-  Tm_Layer layers[1]; // Count: num_layers.
+  Tm_Layer layers[]; // Count: num_layers.
 } Tm_Map;
 
 // -----------------------------------------------------------------------------
@@ -88,28 +88,117 @@ typedef struct Ss_SpriteSheet {
 // Data accessors.
 // -----------------------------------------------------------------------------
 
-/// Return the next tile in the tile set.
-static inline const Ts_Tile* ts_tileset_get_next_tile(
-    const Ts_TileSet* tileset, const Ts_Tile* tile) {
+/// Return the tile set's pixels.
+static inline const Pixel* ts_tileset_get_pixels(const Ts_TileSet* tileset) {
+  assert(tileset);
+  return (const Pixel*)((const uint8_t*)&tileset->tiles[0] +
+                        (tileset->num_tiles * sizeof(Ts_Tile)));
+}
+
+/// Return the ith tile in the tile set.
+static inline const Ts_Tile* ts_tileset_get_tile(
+    const Ts_TileSet* tileset, const int tile) {
+  assert(tileset);
+  assert(tile >= 0);
+  assert(tile < tileset->num_tiles);
+  return &tileset->tiles[tile];
+}
+
+/// Return the ith tile in the tile set.
+static inline Ts_Tile* ts_tileset_get_tile_mut(
+    Ts_TileSet* tileset, const int tile) {
+  return (Ts_Tile*)ts_tileset_get_tile(tileset, tile);
+}
+
+/// Return the ith tile's pixels.
+static inline const Pixel* ts_tileset_get_tile_pixels(
+    const Ts_TileSet* tileset, const int tile) {
   assert(tileset);
+  assert(tile >= 0);
+  assert(tile < tileset->num_tiles);
+  const Pixel*   pixels = ts_tileset_get_pixels(tileset);
+  const Ts_Tile* pTile  = ts_tileset_get_tile(tileset, tile);
+  return (const Pixel*)((const uint8_t*)pixels + pTile->pixels);
+}
+
+/// Return the ith tile's pixels.
+static inline Pixel* ts_tileset_get_tile_pixels_mut(
+    Ts_TileSet* tileset, const int tile) {
+  return (Pixel*)ts_tileset_get_tile_pixels(tileset, tile);
+}
+
+/// Return the ith tile's pixels.
+static inline const Pixel* ts_tile_get_pixels(
+    const Pixel* pixels, const Ts_Tile* tile) {
+  assert(pixels);
   assert(tile);
-  return (const Ts_Tile*)((const uint8_t*)tile + sizeof(Ts_Tile) +
-                          ((tile->width * tile->height - 1) * sizeof(Pixel)));
+  return (const Pixel*)((const uint8_t*)pixels + tile->pixels);
+}
+
+/// Return the tile's pixel at (x,y).
+static const Pixel* ts_tile_xy(
+    const Pixel* tile_pixels, const Ts_Tile* tile, int x, int y) {
+  assert(tile_pixels);
+  assert(tile);
+  assert(x >= 0);
+  assert(y >= 0);
+  assert(x < tile->width);
+  assert(y < tile->height);
+  return &tile_pixels[y * tile->width + x];
+}
+
+/// Return the tile's pixel at (x,y).
+static Pixel* ts_tile_xy_mut(
+    const Pixel* pixels, const Ts_Tile* tile, int x, int y) {
+  return (Pixel*)ts_tile_xy(pixels, tile, x, y);
 }
 
-/// Return the next layer in the tile map.
-static inline const Tm_Layer* tm_map_get_next_layer(
-    const Tm_Map* map, const Tm_Layer* layer) {
+/// Return the ith layer in the tile map.
+static inline const Tm_Layer* tm_map_get_layer(
+    const Tm_Map* map, const int layer) {
   assert(map);
-  assert(layer);
-  return (const Tm_Layer*)((const uint8_t*)layer + sizeof(Tm_Layer) +
-                           ((map->world_width * map->world_height - 1) *
+  assert(layer >= 0);
+  assert(layer < map->num_layers);
+  return (const Tm_Layer*)((const uint8_t*)map->layers +
+                           (layer * map->world_width * map->world_height *
                             sizeof(Tile)));
 }
 
+/// Return the ith layer in the tile map.
+static inline Tm_Layer* tm_map_get_layer_mut(Tm_Map* map, const int layer) {
+  assert(map);
+  assert(layer >= 0);
+  assert(layer < map->num_layers);
+  return (Tm_Layer*)tm_map_get_layer(map, layer);
+}
+
+/// Return the tile in the layer.
+static inline const Tile* tm_layer_get_tile_const_ref(
+    const Tm_Map* map, const Tm_Layer* layer, const int x, const int y) {
+  assert(map);
+  assert(layer);
+  assert(x >= 0);
+  assert(y >= 0);
+  assert(x < map->world_width);
+  assert(y < map->world_height);
+  return &layer->tiles[y * map->world_width + x];
+}
+
+/// Return the tile in the layer.
+static inline Tile tm_layer_get_tile(
+    const Tm_Map* map, const Tm_Layer* layer, const int x, const int y) {
+  return *tm_layer_get_tile_const_ref(map, layer, x, y);
+}
+
+/// Return the tile in the layer.
+static inline Tile* tm_layer_get_tile_mut(
+    Tm_Map* map, Tm_Layer* layer, const int x, const int y) {
+  return (Tile*)tm_layer_get_tile_const_ref(map, layer, x, y);
+}
+
 /// Return the ith row in the sprite sheet.
-static inline const Ss_Row* get_sprite_sheet_row(
-    const Ss_SpriteSheet* sheet, int row) {
+static inline const Ss_Row* ss_get_sprite_sheet_row(
+    const Ss_SpriteSheet* sheet, const int row) {
   assert(sheet);
   assert(row >= 0);
   assert(row < sheet->num_rows);
@@ -120,8 +209,8 @@ static inline const Ss_Row* get_sprite_sheet_row(
 }
 
 /// Return the ith sprite in the row.
-static inline const uint8_t* get_sprite_sheet_sprite(
-    const Ss_SpriteSheet* sheet, const Ss_Row* row, int col) {
+static inline const uint8_t* ss_get_sprite_sheet_sprite(
+    const Ss_SpriteSheet* sheet, const Ss_Row* row, const int col) {
   assert(sheet);
   assert(row);
   assert(col >= 0);
@@ -130,3 +219,13 @@ static inline const uint8_t* get_sprite_sheet_sprite(
   const uint8_t* sprite   = &row->pixels[sprite_offset];
   return sprite;
 }
+
+// -----------------------------------------------------------------------------
+// Validation.
+// -----------------------------------------------------------------------------
+
+/// Validate the tile set.
+bool ts_validate_tileset(const Ts_TileSet* tileset);
+
+/// Validate the map.
+bool tm_validate_map(const Tm_Map* map, const Ts_TileSet* tileset);
diff --git a/include/isogfx/isogfx.h b/include/isogfx/isogfx.h
index 3421a7b..93c6d4e 100644
--- a/include/isogfx/isogfx.h
+++ b/include/isogfx/isogfx.h
@@ -3,26 +3,18 @@
  */
 #pragma once
 
-#include <stdbool.h>
+#include <isogfx/types.h>
+
+#include <stddef.h>
 #include <stdint.h>
 
 typedef struct IsoGfx IsoGfx;
 
 /// Sprite sheet handle.
-typedef uint16_t SpriteSheet;
+typedef uintptr_t SpriteSheet;
 
 /// Sprite handle.
-typedef uint16_t Sprite;
-
-/// Tile handle.
-typedef uint16_t Tile;
-
-/// Colour channel.
-typedef uint8_t Channel;
-
-typedef struct Pixel {
-  Channel r, g, b, a;
-} Pixel;
+typedef uintptr_t Sprite;
 
 typedef enum TileDescType {
   TileFromColour,
@@ -32,32 +24,32 @@ typedef enum TileDescType {
 
 typedef struct TileDesc {
   TileDescType type;
-  int          width;  /// Tile width in pixels.
-  int          height; /// Tile height in pixels.
+  int          width;  // Tile width in pixels.
+  int          height; // Tile height in pixels.
   union {
-    Pixel colour; /// Constant colour tile.
+    Pixel colour; // Constant colour tile.
     struct {
       const char* path;
     } file;
     struct {
-      const uint8_t* data; /// sizeof(Pixel) * width * height
+      const uint8_t* data; // sizeof(Pixel) * width * height
     } mem;
   };
 } TileDesc;
 
 typedef struct WorldDesc {
-  int tile_width;    /// Base tile width in pixels.
-  int tile_height;   /// Base tile height in pixels.
-  int world_width;   /// World width in tiles.
-  int world_height;  /// World height in tiles.
-  int max_num_tiles; /// 0 for an implementation-defined default.
+  int tile_width;   // Base tile width in pixels.
+  int tile_height;  // Base tile height in pixels.
+  int world_width;  // World width in tiles.
+  int world_height; // World height in tiles.
+  int num_tiles;    // Number of tiles to allocate memory for.
 } WorldDesc;
 
 typedef struct IsoGfxDesc {
-  int screen_width;                 /// Screen width in pixels.
-  int screen_height;                /// Screen height in pixels.
-  int max_num_sprites;              /// 0 for an implementation-defined default.
-  int sprite_sheet_pool_size_bytes; /// 0 for an implementation-defined default.
+  void*  memory;        // Block of memory for the engine to use.
+  size_t memory_size;   // Size of memory block in bytes.
+  int    screen_width;  // Screen width in pixels.
+  int    screen_height; // Screen height in pixels.
 } IsoGfxDesc;
 
 /// Create a new isometric graphics engine.
@@ -66,8 +58,11 @@ IsoGfx* isogfx_new(const IsoGfxDesc*);
 /// Destroy the isometric graphics engine.
 void isogfx_del(IsoGfx**);
 
+/// Clear all loaded worlds and sprites.
+void isogfx_clear(IsoGfx*);
+
 /// Create an empty world.
-bool isogfx_make_world(IsoGfx*, const WorldDesc*);
+void isogfx_make_world(IsoGfx*, const WorldDesc*);
 
 /// Load a world from a tile map (.TM) file.
 bool isogfx_load_world(IsoGfx*, const char* filepath);
@@ -88,14 +83,11 @@ void isogfx_set_tile(IsoGfx*, int x, int y, Tile);
 void isogfx_set_tiles(IsoGfx*, int x0, int y0, int x1, int y1, Tile);
 
 /// Load a sprite sheet (.SS) file.
-bool isogfx_load_sprite_sheet(IsoGfx*, const char* filepath, SpriteSheet*);
+SpriteSheet isogfx_load_sprite_sheet(IsoGfx*, const char* filepath);
 
 /// Create an animated sprite.
 Sprite isogfx_make_sprite(IsoGfx*, SpriteSheet);
 
-/// Destroy the sprite.
-void isogfx_del_sprite(IsoGfx*, Sprite);
-
 /// Destroy all the sprites.
 void isogfx_del_sprites(IsoGfx*);
 
@@ -120,9 +112,6 @@ void isogfx_render(IsoGfx*);
 /// position (x,y) instead, use isogfx_set_tile().
 void isogfx_draw_tile(IsoGfx*, int x, int y, Tile);
 
-/// Resize the virtual screen's dimensions.
-bool isogfx_resize(IsoGfx*, int screen_width, int screen_height);
-
 /// Get the virtual screen's dimensions.
 void isogfx_get_screen_size(const IsoGfx*, int* width, int* height);
 
diff --git a/include/isogfx/types.h b/include/isogfx/types.h
new file mode 100644
index 0000000..ce275dc
--- /dev/null
+++ b/include/isogfx/types.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdint.h>
+
+/// Colour channel.
+typedef uint8_t Channel;
+
+/// Pixel.
+typedef struct Pixel {
+  Channel r, g, b, a;
+} Pixel;
+
+/// Tile handle/index.
+typedef uint16_t Tile;
diff --git a/src/asset.c b/src/asset.c
new file mode 100644
index 0000000..98ca083
--- /dev/null
+++ b/src/asset.c
@@ -0,0 +1,34 @@
+#include <isogfx/asset.h>
+
+bool ts_validate_tileset(const Ts_TileSet* tileset) {
+  assert(tileset);
+
+  for (uint16_t i = 0; i < tileset->num_tiles; ++i) {
+    const Ts_Tile* tile = ts_tileset_get_tile(tileset, i);
+    // Tile should be non-empty.
+    if (tile->width == 0) {
+      return false;
+    }
+    if (tile->height == 0) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool tm_validate_map(const Tm_Map* map, const Ts_TileSet* tileset) {
+  assert(map);
+  assert(tileset);
+
+  for (uint16_t t = 0; t < tileset->num_tiles; ++t) {
+    const Ts_Tile* tile = ts_tileset_get_tile(tileset, t);
+    // Tile dimensions should be a multiple of the base tile size.
+    if ((tile->width % map->base_tile_width) != 0) {
+      return false;
+    }
+    if ((tile->height % map->base_tile_height) != 0) {
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/src/isogfx.c b/src/isogfx.c
index 4dff67b..16760ac 100644
--- a/src/isogfx.c
+++ b/src/isogfx.c
@@ -3,27 +3,16 @@
 #include <isogfx/asset.h>
 
 #include <filesystem.h>
-#include <mem.h>
-#include <mempool.h>
+#include <memstack.h>
 #include <path.h>
 
-#include <linux/limits.h>
-
 #include <assert.h>
-#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 
-/// Maximum number of tiles unless the user specifies a value.
-#define DEFAULT_MAX_NUM_TILES 1024
-
-/// Maximum number of sprites unless the user specifies a value.
-#define DEFAULT_MAX_NUM_SPRITES 128
-
-/// Size of sprite sheet pool in bytes unless the user specifies a value.
-#define DEFAULT_SPRITE_SHEET_POOL_SIZE_BYTES (8 * 1024 * 1024)
+/// Maximum path length.
+#define MAX_PATH 256
 
 /// Default animation speed.
 #define ANIMATION_FPS 10
@@ -43,41 +32,27 @@ typedef struct vec2 {
 // Renderer state.
 // -----------------------------------------------------------------------------
 
-typedef struct TileData {
-  uint16_t width;
-  uint16_t height;
-  uint16_t pixels_handle; // Handle to the tile's pixels in the pixel pool.
-} TileData;
-
-typedef struct SpriteData {
-  SpriteSheet sheet; // Handle to the sprite's sheet.
-  ivec2       position;
-  int         animation; // Current animation.
-  int         frame;     // Current frame of animation.
-} SpriteData;
+// TODO: Define a struct Screen with width, height and pixels.
 
-DEF_MEMPOOL_DYN(TilePool, TileData)
-DEF_MEM_DYN(PixelPool, Pixel)
-
-DEF_MEMPOOL_DYN(SpritePool, SpriteData)
-DEF_MEM_DYN(SpriteSheetPool, Ss_SpriteSheet)
+typedef struct SpriteInstance {
+  struct SpriteInstance* next;
+  const Ss_SpriteSheet*  sheet;
+  ivec2                  position;
+  int                    animation; // Current animation.
+  int                    frame;     // Current frame of animation.
+} SpriteInstance;
 
 typedef struct IsoGfx {
   int             screen_width;
   int             screen_height;
-  int             tile_width;
-  int             tile_height;
-  int             world_width;
-  int             world_height;
-  int             max_num_sprites;
-  int             sprite_sheet_pool_size_bytes;
   double          last_animation_time;
-  Tile*           world;
+  Tile            next_tile; // For procedurally-generated tiles.
   Pixel*          screen;
-  TilePool        tiles;
-  PixelPool       pixels;
-  SpritePool      sprites;
-  SpriteSheetPool sheets;
+  Tm_Map*         map;
+  Ts_TileSet*     tileset;
+  SpriteInstance* head_sprite; // Head of sprites list.
+  memstack        stack;
+  size_t          watermark;
 } IsoGfx;
 
 // -----------------------------------------------------------------------------
@@ -114,42 +89,6 @@ static inline vec2 cart2iso(vec2 cart, int s, int t, int w) {
                 .y = (-one_over_s * x + one_over_t * cart.y)};
 }
 
-static const Pixel* tile_xy_const_ref(
-    const IsoGfx* iso, const TileData* tile, int x, int y) {
-  assert(iso);
-  assert(tile);
-  assert(x >= 0);
-  assert(y >= 0);
-  assert(x < tile->width);
-  assert(y < tile->height);
-  return &mem_get_chunk(&iso->pixels, tile->pixels_handle)[y * tile->width + x];
-}
-
-// static Pixel tile_xy(const IsoGfx* iso, const TileData* tile, int x, int y) {
-//   return *tile_xy_const_ref(iso, tile, x, y);
-// }
-
-static Pixel* tile_xy_mut(const IsoGfx* iso, TileData* tile, int x, int y) {
-  return (Pixel*)tile_xy_const_ref(iso, tile, x, y);
-}
-
-static inline const Tile* world_xy_const_ref(const IsoGfx* iso, int x, int y) {
-  assert(iso);
-  assert(x >= 0);
-  assert(y >= 0);
-  assert(x < iso->world_width);
-  assert(y < iso->world_height);
-  return &iso->world[y * iso->world_width + x];
-}
-
-static inline Tile world_xy(const IsoGfx* iso, int x, int y) {
-  return *world_xy_const_ref(iso, x, y);
-}
-
-static inline Tile* world_xy_mut(IsoGfx* iso, int x, int y) {
-  return (Tile*)world_xy_const_ref(iso, x, y);
-}
-
 static inline const Pixel* screen_xy_const_ref(
     const IsoGfx* iso, int x, int y) {
   assert(iso);
@@ -168,15 +107,6 @@ static inline Pixel* screen_xy_mut(IsoGfx* iso, int x, int y) {
   return (Pixel*)screen_xy_const_ref(iso, x, y);
 }
 
-static int calc_num_tile_blocks(
-    int base_tile_width, int base_tile_height, int tile_width,
-    int tile_height) {
-  const int base_tile_size = base_tile_width * base_tile_height;
-  const int tile_size      = tile_width * tile_height;
-  const int num_blocks     = tile_size / base_tile_size;
-  return num_blocks;
-}
-
 // -----------------------------------------------------------------------------
 // Renderer, world and tile management.
 // -----------------------------------------------------------------------------
@@ -188,68 +118,54 @@ IsoGfx* isogfx_new(const IsoGfxDesc* desc) {
   assert((desc->screen_width & 1) == 0);
   assert((desc->screen_height & 1) == 0);
 
-  IsoGfx* iso = calloc(1, sizeof(IsoGfx));
-  if (!iso) {
-    return 0;
+  IsoGfx tmp = {0};
+  if (!memstack_make(&tmp.stack, desc->memory_size, desc->memory)) {
+    goto cleanup;
   }
+  IsoGfx* iso =
+      memstack_alloc_aligned(&tmp.stack, sizeof(IsoGfx), alignof(IsoGfx));
+  *iso = tmp;
 
-  iso->screen_width  = desc->screen_width;
-  iso->screen_height = desc->screen_height;
-
+  iso->screen_width        = desc->screen_width;
+  iso->screen_height       = desc->screen_height;
   iso->last_animation_time = 0.0;
 
-  iso->max_num_sprites = desc->max_num_sprites == 0 ? DEFAULT_MAX_NUM_SPRITES
-                                                    : desc->max_num_sprites;
-  iso->sprite_sheet_pool_size_bytes = desc->sprite_sheet_pool_size_bytes == 0
-                                          ? DEFAULT_SPRITE_SHEET_POOL_SIZE_BYTES
-                                          : desc->sprite_sheet_pool_size_bytes;
+  const size_t screen_size_bytes =
+      desc->screen_width * desc->screen_height * sizeof(Pixel);
+  iso->screen =
+      memstack_alloc_aligned(&iso->stack, screen_size_bytes, alignof(Pixel));
 
-  const int screen_size = desc->screen_width * desc->screen_height;
-  if (!(iso->screen = calloc(screen_size, sizeof(Pixel)))) {
-    goto cleanup;
-  }
+  iso->watermark = memstack_get_watermark(&iso->stack);
 
   return iso;
 
 cleanup:
   isogfx_del(&iso);
-  return 0;
+  return nullptr;
 }
 
-/// Destroy the world, its tile set, and the underlying pools.
-static void destroy_world(IsoGfx* iso) {
+void isogfx_clear(IsoGfx* iso) {
   assert(iso);
-  if (iso->world) {
-    free(iso->world);
-    iso->world = 0;
-  }
-  mempool_del(&iso->tiles);
-  mem_del(&iso->pixels);
-}
-
-/// Destroy all loaded sprites and the underlying pools.
-static void destroy_sprites(IsoGfx* iso) {
-  assert(iso);
-  mempool_del(&iso->sprites);
-  mem_del(&iso->sheets);
-}
-
-void isogfx_del(IsoGfx** pIso) {
-  assert(pIso);
-  IsoGfx* iso = *pIso;
+  iso->last_animation_time = 0.0;
+  iso->next_tile           = 0;
+  iso->map                 = nullptr;
+  iso->tileset             = nullptr;
+  iso->head_sprite         = nullptr;
+  // The base of the stack contains the IsoGfx and the screen buffer. Make sure
+  // we don't clear them.
+  memstack_set_watermark(&iso->stack, iso->watermark);
+}
+
+void isogfx_del(IsoGfx** ppIso) {
+  assert(ppIso);
+  IsoGfx* iso = *ppIso;
   if (iso) {
-    destroy_world(iso);
-    destroy_sprites(iso);
-    if (iso->screen) {
-      free(iso->screen);
-      iso->screen = 0;
-    }
-    free(iso);
-    *pIso = 0;
+    memstack_del(&iso->stack);
+    *ppIso = nullptr;
   }
 }
 
-bool isogfx_make_world(IsoGfx* iso, const WorldDesc* desc) {
+void isogfx_make_world(IsoGfx* iso, const WorldDesc* desc) {
   assert(iso);
   assert(desc);
   assert(desc->tile_width > 0);
@@ -258,36 +174,41 @@ bool isogfx_make_world(IsoGfx* iso, const WorldDesc* desc) {
   // precision.
   assert((desc->tile_width & 1) == 0);
   assert((desc->tile_height & 1) == 0);
-
-  // Handle recreation by destroying the previous world.
-  destroy_world(iso);
-
-  iso->tile_width   = desc->tile_width;
-  iso->tile_height  = desc->tile_height;
-  iso->world_width  = desc->world_width;
-  iso->world_height = desc->world_height;
-
-  const int world_size      = desc->world_width * desc->world_height;
-  const int tile_size       = desc->tile_width * desc->tile_height;
-  const int tile_size_bytes = tile_size * (int)sizeof(Pixel);
-  const int tile_pool_size =
-      desc->max_num_tiles > 0 ? desc->max_num_tiles : DEFAULT_MAX_NUM_TILES;
-
-  if (!(iso->world = calloc(world_size, sizeof(Tile)))) {
-    goto cleanup;
-  }
-  if (!mempool_make_dyn(&iso->tiles, world_size, sizeof(TileData))) {
-    goto cleanup;
-  }
-  if (!mem_make_dyn(&iso->pixels, tile_pool_size, tile_size_bytes)) {
-    goto cleanup;
-  }
-
-  return true;
-
-cleanup:
-  destroy_world(iso);
-  return false;
+  // World must be non-empty.
+  assert(desc->world_width > 0);
+  assert(desc->world_height > 0);
+  // Must have >0 tiles.
+  assert(desc->num_tiles > 0);
+
+  // Handle recreation by destroying the previous world and sprites.
+  isogfx_clear(iso);
+
+  const int    world_size     = desc->world_width * desc->world_height;
+  const size_t map_size_bytes = sizeof(Tm_Map) + (world_size * sizeof(Tile));
+
+  // This implies that all tiles are of the base tile dimensions.
+  // We could enhance the API to allow for supertiles as well. Take in max tile
+  // width and height and allocate enough space using those values.
+  const size_t tile_size            = desc->tile_width * desc->tile_height;
+  const size_t tile_size_bytes      = tile_size * sizeof(Pixel);
+  const size_t tile_data_size_bytes = desc->num_tiles * tile_size_bytes;
+  const size_t tileset_size_bytes   = sizeof(Ts_TileSet) +
+                                    (desc->num_tiles * sizeof(Ts_Tile)) +
+                                    tile_data_size_bytes;
+
+  iso->map  = memstack_alloc_aligned(&iso->stack, map_size_bytes, 4);
+  *iso->map = (Tm_Map){
+      .world_width      = desc->world_width,
+      .world_height     = desc->world_height,
+      .base_tile_width  = desc->tile_width,
+      .base_tile_height = desc->tile_height,
+      .num_layers       = 1,
+  };
+
+  iso->tileset  = memstack_alloc_aligned(&iso->stack, tileset_size_bytes, 4);
+  *iso->tileset = (Ts_TileSet){
+      .num_tiles = desc->num_tiles,
+  };
 }
 
 bool isogfx_load_world(IsoGfx* iso, const char* filepath) {
@@ -296,135 +217,74 @@ bool isogfx_load_world(IsoGfx* iso, const char* filepath) {
 
   bool success = false;
 
-  // Handle recreation by destroying the previous world.
-  destroy_world(iso);
+  // Handle recreation by destroying the previous world and sprites.
+  isogfx_clear(iso);
 
   // Load the map.
   printf("Load tile map: %s\n", filepath);
-  Tm_Map* map = read_file(filepath);
-  if (!map) {
+  WITH_FILE(filepath, {
+    const size_t map_size = get_file_size_f(file);
+    iso->map              = memstack_alloc_aligned(&iso->stack, map_size, 4);
+    success               = read_file_f(file, iso->map);
+  });
+  if (!success) {
     goto cleanup;
   }
+  Tm_Map* const map = iso->map;
 
-  // Allocate memory for the map and tile sets.
-  const int world_size           = map->world_width * map->world_height;
-  const int base_tile_size       = map->base_tile_width * map->base_tile_height;
-  const int base_tile_size_bytes = base_tile_size * (int)sizeof(Pixel);
-  // TODO: Need to get the total number of tiles from the map.
-  const int tile_pool_size = DEFAULT_MAX_NUM_TILES;
-
-  if (!(iso->world = calloc(world_size, sizeof(Tile)))) {
-    goto cleanup;
-  }
-  if (!mempool_make_dyn(&iso->tiles, tile_pool_size, sizeof(TileData))) {
+  // Load the tile set.
+  //
+  // Tile set path is relative to the tile map file. Make it relative to the
+  // current working directory before loading.
+  const char* ts_path               = map->tileset_path;
+  char        ts_path_cwd[MAX_PATH] = {0};
+  if (!path_make_relative(filepath, ts_path, ts_path_cwd, MAX_PATH)) {
     goto cleanup;
   }
-  if (!mem_make_dyn(&iso->pixels, tile_pool_size, base_tile_size_bytes)) {
+  printf("Load tile set: %s\n", ts_path_cwd);
+  WITH_FILE(ts_path_cwd, {
+    const size_t file_size = get_file_size_f(file);
+    iso->tileset           = memstack_alloc_aligned(&iso->stack, file_size, 4);
+    success                = read_file_f(file, iso->tileset);
+  });
+  if (!success) {
+    // TODO: Log errors using the log library.
     goto cleanup;
   }
+  const Ts_TileSet* const tileset = iso->tileset;
+  printf("Loaded tile set (%u tiles): %s\n", tileset->num_tiles, ts_path_cwd);
 
-  // Load the tile sets.
-  const Tm_Layer* layer = &map->layers[0];
-  // TODO: Handle num_layers layers.
-  for (int i = 0; i < 1; ++i) {
-    const char* ts_path = layer->tileset_path;
-
-    // Tile set path is relative to the tile map file. Make it relative to the
-    // current working directory before loading.
-    char ts_path_cwd[PATH_MAX] = {0};
-    if (!path_make_relative(filepath, ts_path, ts_path_cwd, PATH_MAX)) {
-      goto cleanup;
-    }
-
-    Ts_TileSet* tileset = read_file(ts_path_cwd);
-    if (!tileset) {
-      // TODO: Log errors using the log library.
-      goto cleanup;
-    };
-
-    // Load tile data.
-    const Ts_Tile* tile = &tileset->tiles[0];
-    for (uint16_t j = 0; j < tileset->num_tiles; ++j) {
-      // TODO: These checks should be library runtime errors.
-      // Tile dimensions should be a multiple of the base tile size.
-      assert((tile->width % map->base_tile_width) == 0);
-      assert((tile->height % map->base_tile_height) == 0);
-
-      // Allocate N base tile size blocks for the tile.
-      const uint16_t tile_size  = tile->width * tile->height;
-      const int      num_blocks = tile_size / base_tile_size;
-      Pixel*         pixels     = mem_alloc(&iso->pixels, num_blocks);
-      assert(pixels);
-      memcpy(pixels, tile->pixels, tile_size * sizeof(Pixel));
-
-      // Allocate the tile data.
-      TileData* tile_data = mempool_alloc(&iso->tiles);
-      assert(tile_data);
-      tile_data->width  = tile->width;
-      tile_data->height = tile->height;
-      tile_data->pixels_handle =
-          (uint16_t)mem_get_chunk_handle(&iso->pixels, pixels);
-
-      tile = ts_tileset_get_next_tile(tileset, tile);
-    }
-
-    printf("Loaded tile set (%u tiles): %s\n", tileset->num_tiles, ts_path_cwd);
-
-    free(tileset);
-    layer = tm_map_get_next_layer(map, layer);
-  }
-
-  // Load the map into the world.
-  layer = &map->layers[0];
-  // TODO: Handle num_layers layers.
-  for (int i = 0; i < 1; ++i) {
-    memcpy(iso->world, layer->tiles, world_size * sizeof(Tile));
-
-    // TODO: We need to handle 'firsgid' in TMX files.
-    for (int j = 0; j < world_size; ++j) {
-      iso->world[j] -= 1;
-    }
-
-    layer = tm_map_get_next_layer(map, layer);
-  }
-
-  iso->world_width  = map->world_width;
-  iso->world_height = map->world_height;
-  iso->tile_width   = map->base_tile_width;
-  iso->tile_height  = map->base_tile_height;
+  // TODO: These assertions on input data should be library runtime errors.
+  assert(ts_validate_tileset(tileset));
+  assert(tm_validate_map(map, tileset));
 
   success = true;
 
 cleanup:
-  if (map) {
-    free(map);
-  }
   if (!success) {
-    destroy_world(iso);
+    isogfx_clear(iso);
   }
   return success;
 }
 
 int isogfx_world_width(const IsoGfx* iso) {
   assert(iso);
-  return iso->world_width;
+  return iso->map->world_width;
 }
 
 int isogfx_world_height(const IsoGfx* iso) {
   assert(iso);
-  return iso->world_height;
+  return iso->map->world_height;
 }
 
-/// Create a tile mask procedurally.
 static void make_tile_from_colour(
-    const IsoGfx* iso, Pixel colour, TileData* tile) {
-  assert(iso);
+    Pixel colour, const Ts_Tile* tile, Pixel* tile_pixels) {
   assert(tile);
+  assert(tile_pixels);
 
   const int width  = tile->width;
   const int height = tile->height;
   const int r      = width / height;
-
   for (int y = 0; y < height / 2; ++y) {
     const int mask_start = width / 2 - r * y - 1;
     const int mask_end   = width / 2 + r * y + 1;
@@ -433,11 +293,11 @@ static void make_tile_from_colour(
       const Pixel val = mask ? colour : (Pixel){.r = 0, .g = 0, .b = 0, .a = 0};
 
       // Top half.
-      *tile_xy_mut(iso, tile, x, y) = val;
+      *ts_tile_xy_mut(tile_pixels, tile, x, y) = val;
 
       // Bottom half reflects the top half.
-      const int y_reflected                   = height - y - 1;
-      *tile_xy_mut(iso, tile, x, y_reflected) = val;
+      const int y_reflected                              = height - y - 1;
+      *ts_tile_xy_mut(tile_pixels, tile, x, y_reflected) = val;
     }
   }
 }
@@ -445,41 +305,58 @@ static void make_tile_from_colour(
 Tile isogfx_make_tile(IsoGfx* iso, const TileDesc* desc) {
   assert(iso);
   assert(desc);
-  // Client must create world before creating tiles.
-  assert(iso->tile_width > 0);
-  assert(iso->tile_height > 0);
+  // Client must create a world first.
+  assert(iso->map);
+  assert(iso->tileset);
+  // Currently, procedural tiles must match the base tile size.
+  assert(desc->width == iso->map->base_tile_width);
+  assert(desc->height == iso->map->base_tile_height);
+  // Cannot exceed max tiles.
+  assert(iso->next_tile < iso->tileset->num_tiles);
 
-  TileData* tile = mempool_alloc(&iso->tiles);
-  assert(tile); // TODO: Make this a hard assert.
+  const Tile tile = iso->next_tile++;
 
-  const int num_blocks = calc_num_tile_blocks(
-      iso->tile_width, iso->tile_height, desc->width, desc->height);
+  const size_t tile_size_bytes = desc->width * desc->height * sizeof(Pixel);
 
-  Pixel* pixels = mem_alloc(&iso->pixels, num_blocks);
-  assert(pixels); // TODO: Make this a hard assert.
+  switch (desc->type) {
+  case TileFromColour: {
+    assert(desc->width > 0);
+    assert(desc->height > 0);
 
-  tile->width         = desc->width;
-  tile->height        = desc->height;
-  tile->pixels_handle = mem_get_chunk_handle(&iso->pixels, pixels);
+    Ts_Tile* const ts_tile = ts_tileset_get_tile_mut(iso->tileset, tile);
 
-  switch (desc->type) {
-  case TileFromColour:
-    make_tile_from_colour(iso, desc->colour, tile);
+    *ts_tile = (Ts_Tile){
+        .width  = iso->map->base_tile_width,
+        .height = iso->map->base_tile_height,
+        .pixels = tile * tile_size_bytes,
+    };
+
+    Pixel* const tile_pixels =
+        ts_tileset_get_tile_pixels_mut(iso->tileset, tile);
+    make_tile_from_colour(desc->colour, ts_tile, tile_pixels);
     break;
+  }
   case TileFromFile:
     assert(false); // TODO
     break;
-  case TileFromMemory:
+  case TileFromMemory: {
+    assert(desc->width > 0);
+    assert(desc->height > 0);
     assert(false); // TODO
     break;
   }
+  }
 
-  return (Tile)mempool_get_block_index(&iso->tiles, tile);
+  return tile;
 }
 
 void isogfx_set_tile(IsoGfx* iso, int x, int y, Tile tile) {
   assert(iso);
-  *world_xy_mut(iso, x, y) = tile;
+
+  Tm_Layer* const layer    = tm_map_get_layer_mut(iso->map, 0);
+  Tile*           map_tile = tm_layer_get_tile_mut(iso->map, layer, x, y);
+
+  *map_tile = tile;
 }
 
 void isogfx_set_tiles(IsoGfx* iso, int x0, int y0, int x1, int y1, Tile tile) {
@@ -491,88 +368,67 @@ void isogfx_set_tiles(IsoGfx* iso, int x0, int y0, int x1, int y1, Tile tile) {
   }
 }
 
-bool isogfx_load_sprite_sheet(
-    IsoGfx* iso, const char* filepath, SpriteSheet* p_sheet) {
+SpriteSheet isogfx_load_sprite_sheet(IsoGfx* iso, const char* filepath) {
   assert(iso);
   assert(filepath);
-  assert(p_sheet);
 
-  bool success = false;
-
-  // Lazy initialization of sprite pools.
-  if (mempool_capacity(&iso->sprites) == 0) {
-    if (!mempool_make_dyn(
-            &iso->sprites, iso->max_num_sprites, sizeof(SpriteData))) {
-      return false;
-    }
-  }
-  if (mem_capacity(&iso->sheets) == 0) {
-    // Using a block size of 1 byte for sprite sheet data.
-    if (!mem_make_dyn(&iso->sheets, iso->sprite_sheet_pool_size_bytes, 1)) {
-      return false;
-    }
-  }
+  bool         success     = false;
+  SpriteSheet  spriteSheet = 0;
+  const size_t watermark   = memstack_get_watermark(&iso->stack);
 
   // Load sprite sheet file.
   printf("Load sprite sheet: %s\n", filepath);
-  FILE* file = fopen(filepath, "rb");
-  if (file == NULL) {
-    goto cleanup;
-  }
-  const size_t    sheet_size = get_file_size(file);
-  Ss_SpriteSheet* ss_sheet   = mem_alloc(&iso->sheets, sheet_size);
-  if (!ss_sheet) {
-    goto cleanup;
-  }
-  if (fread(ss_sheet, sheet_size, 1, file) != 1) {
+  Ss_SpriteSheet* ss_sheet = nullptr;
+  WITH_FILE(filepath, {
+    const size_t file_size = get_file_size_f(file);
+    ss_sheet =
+        memstack_alloc_aligned(&iso->stack, file_size, alignof(Ss_SpriteSheet));
+    success = read_file_f(file, ss_sheet);
+  });
+  if (!success) {
     goto cleanup;
   }
+  assert(ss_sheet);
 
-  *p_sheet = mem_get_chunk_handle(&iso->sheets, ss_sheet);
-  success  = true;
+  spriteSheet = (SpriteSheet)ss_sheet;
 
 cleanup:
-  // Pools remain initialized since client may attempt to load other sprites.
-  if (file != NULL) {
-    fclose(file);
-  }
   if (!success) {
     if (ss_sheet) {
-      mem_free(&iso->sheets, &ss_sheet);
+      memstack_set_watermark(&iso->stack, watermark);
     }
   }
-  return success;
+  return spriteSheet;
 }
 
 Sprite isogfx_make_sprite(IsoGfx* iso, SpriteSheet sheet) {
   assert(iso);
+  assert(sheet);
 
-  SpriteData* sprite = mempool_alloc(&iso->sprites);
-  assert(sprite);
+  // TODO: Remove memstack_alloc() and replace it with a same-name macro that
+  //  calls memstack_alloc_aligned() with sizeof/alignof. No real point in
+  //  having unaligned allocations.
+  SpriteInstance* sprite = memstack_alloc_aligned(
+      &iso->stack, sizeof(SpriteInstance), alignof(SpriteInstance));
 
-  sprite->sheet = sheet;
+  sprite->sheet    = (const Ss_SpriteSheet*)sheet;
+  sprite->next     = iso->head_sprite;
+  iso->head_sprite = sprite;
 
-  return mempool_get_block_index(&iso->sprites, sprite);
+  return (Sprite)sprite;
 }
 
-#define with_sprite(SPRITE, BODY)                                \
-  {                                                              \
-    SpriteData* data = mempool_get_block(&iso->sprites, sprite); \
-    assert(data);                                                \
-    BODY;                                                        \
-  }
-
-void isogfx_set_sprite_position(IsoGfx* iso, Sprite sprite, int x, int y) {
+void isogfx_set_sprite_position(IsoGfx* iso, Sprite hSprite, int x, int y) {
   assert(iso);
-  with_sprite(sprite, {
-    data->position.x = x;
-    data->position.y = y;
-  });
+  SpriteInstance* sprite = (SpriteInstance*)hSprite;
+  sprite->position.x     = x;
+  sprite->position.y     = y;
 }
 
-void isogfx_set_sprite_animation(IsoGfx* iso, Sprite sprite, int animation) {
+void isogfx_set_sprite_animation(IsoGfx* iso, Sprite hSprite, int animation) {
   assert(iso);
-  with_sprite(sprite, { data->animation = animation; });
+  SpriteInstance* sprite = (SpriteInstance*)hSprite;
+  sprite->animation      = animation;
 }
 
 void isogfx_update(IsoGfx* iso, double t) {
@@ -586,14 +442,14 @@ void isogfx_update(IsoGfx* iso, double t) {
   }
 
   if ((t - iso->last_animation_time) >= ANIMATION_UPDATE_DELTA) {
-    // TODO: Consider linking animated sprites in a list so that we only walk
-    // over those here and not also the static sprites.
-    mempool_foreach(&iso->sprites, sprite, {
-      const Ss_SpriteSheet* sheet = mem_get_chunk(&iso->sheets, sprite->sheet);
-      assert(sheet); // TODO: Make this a hard assert inside the mem/pool.
-      const Ss_Row* row = get_sprite_sheet_row(sheet, sprite->animation);
+    // TODO: Consider linking animated sprites in a separate list so that we
+    //  only walk over those here and not also the static sprites.
+    for (SpriteInstance* sprite = iso->head_sprite; sprite;
+         sprite                 = sprite->next) {
+      const Ss_SpriteSheet* sheet = sprite->sheet;
+      const Ss_Row* row = ss_get_sprite_sheet_row(sheet, sprite->animation);
       sprite->frame     = (sprite->frame + 1) % row->num_cols;
-    });
+    }
 
     iso->last_animation_time = t;
   }
@@ -614,8 +470,10 @@ typedef struct CoordSystem {
 static CoordSystem make_iso_coord_system(const IsoGfx* iso) {
   assert(iso);
   const ivec2 o = {iso->screen_width / 2, 0};
-  const ivec2 x = {.x = iso->tile_width / 2, .y = iso->tile_height / 2};
-  const ivec2 y = {.x = -iso->tile_width / 2, .y = iso->tile_height / 2};
+  const ivec2 x = {
+      .x = iso->map->base_tile_width / 2, .y = iso->map->base_tile_height / 2};
+  const ivec2 y = {
+      .x = -iso->map->base_tile_width / 2, .y = iso->map->base_tile_height / 2};
   return (CoordSystem){o, x, y};
 }
 
@@ -696,19 +554,20 @@ static void draw_rect(
 ///     World (0, 0) -> (screen_width / 2, 0).
 static void draw_tile(IsoGfx* iso, ivec2 screen_origin, Tile tile) {
   assert(iso);
+  assert(iso->tileset);
 
-  const TileData* tile_data = mempool_get_block(&iso->tiles, tile);
-  assert(tile_data);
-  const Pixel* pixels = tile_xy_const_ref(iso, tile_data, 0, 0);
+  const Ts_Tile* pTile  = ts_tileset_get_tile(iso->tileset, tile);
+  const Pixel*   pixels = ts_tileset_get_tile_pixels(iso->tileset, tile);
 
   // Move from the top diamond-corner to the top-left corner of the tile image.
   // For regular tiles, tile height == base tile height, so the y offset is 0.
   // For super tiles, move as high up as the height of the tile.
   const ivec2 offset = {
-      -(iso->tile_width / 2), tile_data->height - iso->tile_height};
+      -(iso->map->base_tile_width / 2),
+      pTile->height - iso->map->base_tile_height};
   const ivec2 top_left = ivec2_add(screen_origin, offset);
 
-  draw_rect(iso, top_left, tile_data->width, tile_data->height, pixels, 0);
+  draw_rect(iso, top_left, pTile->width, pTile->height, pixels, 0);
 }
 
 static void draw_world(IsoGfx* iso) {
@@ -721,14 +580,16 @@ static void draw_world(IsoGfx* iso) {
 
   const CoordSystem iso_space = make_iso_coord_system(iso);
 
+  const Tm_Layer* layer = tm_map_get_layer(iso->map, 0);
+
   // TODO: Culling.
   // Ex: map the screen corners to tile space to cull.
   // Ex: walk in screen space and fetch the tile.
   // The tile-centric approach might be more cache-friendly since the
   // screen-centric approach would juggle multiple tiles throughout the scan.
-  for (int wy = 0; wy < iso->world_height; ++wy) {
-    for (int wx = 0; wx < iso->world_width; ++wx) {
-      const Tile  tile          = world_xy(iso, wx, wy);
+  for (int wy = 0; wy < iso->map->world_height; ++wy) {
+    for (int wx = 0; wx < iso->map->world_width; ++wx) {
+      const Tile  tile          = tm_layer_get_tile(iso->map, layer, wx, wy);
       const ivec2 screen_origin = GetTileScreenOrigin(iso_space, wx, wy);
       draw_tile(iso, screen_origin, tile);
     }
@@ -736,7 +597,7 @@ static void draw_world(IsoGfx* iso) {
 }
 
 static void draw_sprite(
-    IsoGfx* iso, ivec2 origin, const SpriteData* sprite,
+    IsoGfx* iso, ivec2 origin, const SpriteInstance* sprite,
     const Ss_SpriteSheet* sheet) {
   assert(iso);
   assert(sprite);
@@ -745,8 +606,8 @@ static void draw_sprite(
   assert(sprite->animation < sheet->num_rows);
   assert(sprite->frame >= 0);
 
-  const Ss_Row*  row   = get_sprite_sheet_row(sheet, sprite->animation);
-  const uint8_t* frame = get_sprite_sheet_sprite(sheet, row, sprite->frame);
+  const Ss_Row*  row   = ss_get_sprite_sheet_row(sheet, sprite->animation);
+  const uint8_t* frame = ss_get_sprite_sheet_sprite(sheet, row, sprite->frame);
   draw_rect(
       iso, origin, sheet->sprite_width, sheet->sprite_height,
       sheet->palette.colours, frame);
@@ -757,14 +618,15 @@ static void draw_sprites(IsoGfx* iso) {
 
   const CoordSystem iso_space = make_iso_coord_system(iso);
 
-  mempool_foreach(&iso->sprites, sprite, {
-    const Ss_SpriteSheet* sheet = mem_get_chunk(&iso->sheets, sprite->sheet);
+  for (const SpriteInstance* sprite = iso->head_sprite; sprite;
+       sprite                       = sprite->next) {
+    const Ss_SpriteSheet* sheet = sprite->sheet;
     assert(sheet);
 
     const ivec2 screen_origin =
         GetTileScreenOrigin(iso_space, sprite->position.x, sprite->position.y);
     draw_sprite(iso, screen_origin, sprite, sheet);
-  });
+  }
 }
 
 void isogfx_render(IsoGfx* iso) {
@@ -777,35 +639,14 @@ void isogfx_draw_tile(IsoGfx* iso, int x, int y, Tile tile) {
   assert(iso);
   assert(x >= 0);
   assert(y >= 0);
-  assert(x < iso->world_width);
-  assert(y < iso->world_height);
+  assert(x < iso->map->world_width);
+  assert(y < iso->map->world_height);
 
   const CoordSystem iso_space     = make_iso_coord_system(iso);
   const ivec2       screen_origin = GetTileScreenOrigin(iso_space, x, y);
   draw_tile(iso, screen_origin, tile);
 }
 
-bool isogfx_resize(IsoGfx* iso, int screen_width, int screen_height) {
-  assert(iso);
-  assert(iso->screen);
-
-  const int current_size = iso->screen_width * iso->screen_height;
-  const int new_size     = screen_width * screen_height;
-
-  if (new_size > current_size) {
-    Pixel* new_screen = calloc(new_size, sizeof(Pixel));
-    if (new_screen) {
-      free(iso->screen);
-      iso->screen = new_screen;
-    } else {
-      return false;
-    }
-  }
-  iso->screen_width  = screen_width;
-  iso->screen_height = screen_height;
-  return true;
-}
-
 void isogfx_get_screen_size(const IsoGfx* iso, int* width, int* height) {
   assert(iso);
   assert(width);
@@ -826,11 +667,11 @@ void isogfx_pick_tile(
   assert(yiso);
 
   const vec2 xy_iso = cart2iso(
-      (vec2){.x = xcart, .y = ycart}, iso->tile_width, iso->tile_height,
-      iso->screen_width);
+      (vec2){.x = xcart, .y = ycart}, iso->map->base_tile_width,
+      iso->map->base_tile_height, iso->screen_width);
 
-  if ((0 <= xy_iso.x) && (xy_iso.x < iso->world_width) && (0 <= xy_iso.y) &&
-      (xy_iso.y < iso->world_height)) {
+  if ((0 <= xy_iso.x) && (xy_iso.x < iso->map->world_width) &&
+      (0 <= xy_iso.y) && (xy_iso.y < iso->map->world_height)) {
     *xiso = (int)xy_iso.x;
     *yiso = (int)xy_iso.y;
   } else {
diff --git a/tools/mkasset.py b/tools/mkasset.py
index fd2ead7..ae27ead 100644
--- a/tools/mkasset.py
+++ b/tools/mkasset.py
@@ -51,10 +51,15 @@ def convert_tsx(input_filepath, output_filepath):
     print(f"Max width:  {max_tile_width}")
     print(f"Max height: {max_tile_height}")
 
+    pixels = []  # List of byte arrays
+    pixels_offset = 0
+
     with open(output_filepath, 'bw') as output:
+        # Write the header.
         output.write(ctypes.c_uint16(tile_count))
-        output.write(ctypes.c_uint16(max_tile_width))
-        output.write(ctypes.c_uint16(max_tile_height))
+        # output.write(ctypes.c_uint16(max_tile_width))
+        # output.write(ctypes.c_uint16(max_tile_height))
+        output.write(ctypes.c_uint16(0))  # Pad.
 
         num_tile = 0
         for tile in root:
@@ -72,12 +77,23 @@ def convert_tsx(input_filepath, output_filepath):
             tile_height = int(image.attrib["height"])
             tile_path = image.attrib["source"]
 
-            output.write(ctypes.c_uint16(tile_width))
-            output.write(ctypes.c_uint16(tile_height))
+            assert (tile_width > 0)
+            assert (tile_height > 0)
 
+            tile_pixels_offset = pixels_offset
             with Image.open(tile_path) as im:
                 bytes = im.convert('RGBA').tobytes()
-                output.write(bytes)
+                pixels.append(bytes)
+                pixels_offset += len(bytes)
+
+            # Write the tile.
+            output.write(ctypes.c_uint16(tile_width))
+            output.write(ctypes.c_uint16(tile_height))
+            output.write(ctypes.c_uint32(tile_pixels_offset))
+
+        # Write the pixel data.
+        for bytes in pixels:
+            output.write(bytes)
 
 
 def convert_tmx(input_filepath, output_filepath):
@@ -96,23 +112,27 @@ def convert_tmx(input_filepath, output_filepath):
     print(f"Tile width:  {base_tile_width}")
     print(f"Tile height: {base_tile_height}")
 
-    with open(output_filepath, 'bw') as output:
-        output.write(ctypes.c_uint16(map_width))
-        output.write(ctypes.c_uint16(map_height))
-        output.write(ctypes.c_uint16(base_tile_width))
-        output.write(ctypes.c_uint16(base_tile_height))
-        output.write(ctypes.c_uint16(num_layers))
-
-        tileset_path = None
+    tileset_path = None
 
+    with open(output_filepath, 'bw') as output:
         for child in root:
             if child.tag == "tileset":
+                assert (not tileset_path)  # Only supporting one tile set per map right now.
+
                 tileset = child
                 tileset_path = tileset.attrib["source"]
 
                 print(f"Tile set: {tileset_path}")
 
                 tileset_path = tileset_path.replace("tsx", "ts")
+
+                # Write the header.
+                output.write(to_char_array(tileset_path, MAX_PATH_LENGTH))
+                output.write(ctypes.c_uint16(map_width))
+                output.write(ctypes.c_uint16(map_height))
+                output.write(ctypes.c_uint16(base_tile_width))
+                output.write(ctypes.c_uint16(base_tile_height))
+                output.write(ctypes.c_uint16(num_layers))
             elif child.tag == "layer":
                 layer = child
                 layer_id = int(layer.attrib["id"])
@@ -123,9 +143,6 @@ def convert_tmx(input_filepath, output_filepath):
                 print(f"Width:  {layer_width}")
                 print(f"Height: {layer_height}")
 
-                assert (tileset_path)
-                output.write(to_char_array(tileset_path, MAX_PATH_LENGTH))
-
                 # Assume the layer's dimensions matches the map's.
                 assert (layer_width == map_width)
                 assert (layer_height == map_height)
@@ -139,7 +156,9 @@ def convert_tmx(input_filepath, output_filepath):
                 for row in rows:
                     tile_ids = [x.strip() for x in row.split(',') if x]
                     for tile_id in tile_ids:
-                        output.write(ctypes.c_uint16(int(tile_id)))
+                        # TODO: We need to handle 'firsgid' in TMX files.
+                        #  For now, assume it's 1 and do -1 to make the tiles 0-based.
+                        output.write(ctypes.c_uint16(int(tile_id) - 1))
 
 
 def get_num_cols(image, sprite_width):