diff --git a/include/api.h b/include/api.h
new file mode 100644
index 0000000..ab351fe
--- /dev/null
+++ b/include/api.h
@@ -0,0 +1,138 @@
+#ifndef _API_H
+#define _API_H
+
+#include <stdafx.h>
+#include <vecmath.h>
+
+typedef int Error;
+
+#define ERROR_NONE 0
+#define ERROR_OUT_OF_MEMORY 1
+#define ERROR_OUT_OF_BLOCKS 2
+#define ERROR_OUT_OF_MATERIALS 3
+#define ERROR_OUT_OF_TEXTURES 4
+
+typedef int Orientation;
+
+#define ORIENTATION_NEGATIVE_X ~0
+#define ORIENTATION_POSITIVE_X 0
+#define ORIENTATION_NEGATIVE_Y ~1
+#define ORIENTATION_POSITIVE_Y 1
+#define ORIENTATION_NEGATIVE_Z ~2
+#define ORIENTATION_POSITIVE_Z 2
+
+#define ORIENTATION_INIT_SIGN_INDEX(sign, index) ((sign) > 0 ? (index) : ~(index))
+#define ORIENTATION_GET_INDEX(orientation) ((orientation) & 0x4 ? ~(orientation) : (orientation))
+#define ORIENTATION_GET_SIGN(orientation) ((oritentation) & 0x4 ? -1 : 1)
+
+typedef int Transform;
+
+#define TRANSFORM_IDENTITY 0
+#define TRANSFORM_ROTATE_CW 1
+#define TRANSFORM_ROTATE_CCW 2
+#define TRANSFORM_ROTATE_180 3
+#define TRANSFORM_MIRROR 4
+#define TRANSFORM_MIRROR_ROTATE_CW 5
+#define TRANSFORM_MIRROR_ROTATE_CCW 6
+#define TRANSFORM_MIRROR_ROTATE_180 7
+
+typedef unsigned short BlockId;
+
+#define BLOCK_ID_AIR 0
+
+typedef unsigned short MaterialId;
+
+#define MATERIAL_ID_EMPTY 0
+
+typedef unsigned short TextureId;
+
+#define TEXTURE_ID_EMPTY_BASE_COLOR 0
+#define TEXTURE_ID_EMPTY_EMISSIVE 1
+#define TEXTURE_ID_EMPTY_NORMAL 2
+#define TEXTURE_ID_EMPTY_OCCLUSION_ROUGHNESS_METALLIC 3
+
+typedef int TextureUsage;
+
+#define TEXTURE_USAGE_BASE_COLOR 0
+#define TEXTURE_USAGE_NORMAL 1
+#define TEXTURE_USAGE_OCCLUSION_ROUGHNESS_METALLIC 2
+#define TEXTURE_USAGE_EMISSIVE 3
+
+typedef struct String {
+    const char* ptr;
+    size_t len;
+} String;
+
+#define STRING_NULL (String){ .ptr = NULL, .len = 0 }
+
+typedef struct BlockDefinitionWall {
+    MaterialId material;
+    Transform transform;
+} BlockDefinitionWall;
+
+typedef struct BlockDefinitionWalls {
+    BlockDefinitionWall negative_x;
+    BlockDefinitionWall positive_x;
+    BlockDefinitionWall negative_y;
+    BlockDefinitionWall positive_y;
+    BlockDefinitionWall negative_z;
+    BlockDefinitionWall positive_z;
+} BlockDefinitionWalls;
+
+typedef struct BlockDefinition {
+    BlockDefinitionWalls walls;
+} BlockDefinition;
+
+typedef struct MaterialDefinition {
+    vec3_t base_color;
+    vec3_t emissive;
+    float ior;
+    float metallic;
+    float normal_scale;
+    float occlusion_texture_strength;
+    float roughness;
+
+    TextureId base_color_texture;
+    TextureId emissive_texture;
+    TextureId normal_texture;
+    TextureId occlusion_roughness_metallic_texture;
+} MaterialDefinition;
+
+typedef struct TextureData {
+    TextureUsage usage;
+    unsigned int width;
+    unsigned int height;
+    const char *data;
+} TextureData;
+
+typedef struct TextureDataMutable {
+    TextureUsage usage;
+    unsigned int width;
+    unsigned int height;
+    char *data;
+} TextureDataMutable;
+
+Error BlockIdFromName(String name, bool *exists, BlockId *out);
+Error BlockDefinitionFromId(BlockId id, const BlockDefinition **out);
+Error BlockDefine(String name, const BlockDefinition *definition, BlockId *out);
+
+Error MaterialIdFromName(String name, bool *exists, MaterialId *out);
+Error MaterialDefinitionFromId(MaterialId, const MaterialDefinition **out);
+Error MaterialDefine(String name, const MaterialDefinition *definition, MaterialId *out);
+
+Error TextureIdFromName(String name, TextureUsage usage, bool *exists, TextureId *out);
+Error TextureDefine(String name, const TextureData *texture_data, TextureId *out);
+
+Error TextureResize(TextureDataMutable *texture_data, unsigned int width, unsigned int height);
+
+// --- CALLBACKS ---
+
+void PreInit();
+void PostInit();
+void Deinit();
+
+void FilterBlock(BlockId id, String name, bool *exists, BlockDefinition *definition);
+void FilterMaterial(MaterialId id, String name, bool *exists, MaterialDefinition *definition);
+void FilterTexture(TextureId id, String name, bool *exists, TextureDataMutable *texture_data);
+
+#endif
diff --git a/include/stdafx.h b/include/stdafx.h
new file mode 100644
index 0000000..c06d92e
--- /dev/null
+++ b/include/stdafx.h
@@ -0,0 +1,27 @@
+#ifndef _STDAFX_H
+#define _STDAFX_H
+
+typedef unsigned long size_t;
+typedef long ssize_t;
+typedef long ptrdiff_t;
+typedef long intptr_t;
+typedef unsigned long uintptr_t;
+
+#define NULL ((void *)0)
+
+#define bool _Bool
+#define true 1
+#define false 0
+#define __bool_true_false_are_defined 1
+
+typedef signed char int8_t;
+typedef short int16_t;
+typedef int int32_t;
+typedef long int64_t;
+
+typedef unsigned char uint8_t;
+typedef unsigned short uint16_t;
+typedef unsigned int uint32_t;
+typedef unsigned long uint64_t;
+
+#endif
diff --git a/include/vecmath.h b/include/vecmath.h
new file mode 100644
index 0000000..7f59690
--- /dev/null
+++ b/include/vecmath.h
@@ -0,0 +1,58 @@
+#ifndef _VECMATH_H
+#define _VECMATH_H
+
+typedef union vec2_t {
+    struct {
+        float x;
+        float y;
+    };
+    float v[2];
+} vec2_t;
+
+typedef union vec3_t {
+    struct {
+        float x;
+        float y;
+        float z;
+    };
+    float v[3];
+} vec3_t;
+
+typedef union vec4_t {
+    struct {
+        float x;
+        float y;
+        float z;
+        float w;
+    };
+    float v[4];
+} vec4_t;
+
+typedef union ivec2_t {
+    struct {
+        int x;
+        int y;
+    };
+    int v[2];
+} vec2_t;
+
+typedef union ivec3_t {
+    struct {
+        int x;
+        int y;
+        int z;
+    };
+    int v[3];
+} vec3_t;
+
+typedef union ivec4_t {
+    struct {
+        int x;
+        int y;
+        int z;
+        int w;
+    };
+    int v[4];
+} vec4_t;
+
+#endif
diff --git a/src/assets/Textures.zig b/src/assets/Textures.zig
index fd76300..a6ff3f3 100644
--- a/src/assets/Textures.zig
+++ b/src/assets/Textures.zig
@@ -141,7 +141,7 @@ pub fn deinit(self: *Textures, engine: *Engine, allocator: std.mem.Allocator) vo
 /// Get the ID of a texture given its filename (as a string) and usage. Returns
 /// `null` if such texture hasn't been loaded. When the filename is `null`,
 /// returns an empty texture ID appropriate for given usage.
-pub fn get(self: *const Textures, maybe_filename: []const u8, usage: Texture.Usage) ?Id {
+pub fn get(self: *const Textures, maybe_filename: ?[]const u8, usage: Texture.Usage) ?Id {
     if (maybe_filename) |filename| {
         return self.map.get(.{
             // If the atom doesn't exist, then the texture cannot possibly exist.
diff --git a/src/voxels.zig b/src/voxels.zig
index 92f7cfc..e24c9f9 100644
--- a/src/voxels.zig
+++ b/src/voxels.zig
@@ -51,14 +51,14 @@ pub const Orientation = enum(u3) {
 };
 
 pub const Transform = enum(u3) {
-    identity,
-    rotate_cw,
-    rotate_ccw,
-    rotate_180,
-    mirror,
-    mirror_rotate_cw,
-    mirror_rotate_ccw,
-    mirror_rotate_180,
+    identity = 0,
+    rotate_cw = 1,
+    rotate_ccw = 2,
+    rotate_180 = 3,
+    mirror = 4,
+    mirror_rotate_cw = 5,
+    mirror_rotate_ccw = 6,
+    mirror_rotate_180 = 7,
 };
 
 //  ┌──────────────────── x