diff --git a/include/arena.h b/include/arena.h
index 8933e7b..3978c7c 100644
--- a/include/arena.h
+++ b/include/arena.h
@@ -1,4 +1,39 @@
 #ifndef ARENA_H
 #define ARENA_H
 
+#include <stdint.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <stdbool.h>
+
+typedef struct {
+    void *data;
+    size_t size;
+    size_t offset;
+} Arena;
+
+typedef enum {
+    ARENA_OK,
+    ARENA_BAD_ALLOC,
+    ARENA_OUT_OF_SPACE,
+    ARENA_NULL_ARG,
+} ArenaErr;
+
+typedef struct {
+    bool is_valid;
+    union {
+        ArenaErr err;
+        void *pointer;
+    };
+} ArenaPointer;
+
+Arena arena_init(void *buffer, size_t size);
+void arena_destroy(Arena *arena);
+
+ArenaPointer arena_alloc(Arena *arena, size_t size, size_t alignment);
+ArenaPointer arena_push(Arena *arena, void *data);
+ArenaErr arena_realloc(Arena *arena, size_t new_size);
+
+size_t align_arena_offset(Arena *arena, size_t alignment);
+
 #endif // !ARENA_H