diff --git a/src/main.c b/src/main.c
index 4508a7d..4c98781 100644
--- a/src/main.c
+++ b/src/main.c
@@ -21,6 +21,11 @@
 #define ARENA_IMPLEMENTATION
 #include <tsoding/arena.h>
 
+#include "string.h"
+
+#define ED_UI_IMPLEMENTATION
+#include "ui.h"
+
 static Arena default_arena = {0};
 static Arena temporary_arena = {0};
 static Arena *context_arena = &default_arena;
@@ -91,13 +96,7 @@ static struct {
     bool should_exit;
 } state;
 
-#define _String(text) ((String) { .data = text, .len = sizeof(text) })
-typedef struct {
-    char *data;
-    size_t len;
-} String;
-
-void queue_text(String text, float position[2]) {
+void queue_text(string text, float position[2]) {
     float x = 0;
     for (size_t i=0; i < text.len; ++i) {
         if (text.data[i] >= 32 && text.data[i] <= 32+95) {
diff --git a/src/string.h b/src/string.h
new file mode 100644
index 0000000..6571cbd
--- /dev/null
+++ b/src/string.h
@@ -0,0 +1,13 @@
+#ifndef ED_STRING_INCLUDED
+#define ED_STRING_INCLUDED
+
+#include <stddef.h>
+
+#define _String(text) ((string) { .data = text, .len = sizeof(text) })
+typedef struct {
+    char *data;
+    size_t len;
+} string;
+
+#endif
+
diff --git a/src/ui.h b/src/ui.h
new file mode 100644
index 0000000..fd01b17
--- /dev/null
+++ b/src/ui.h
@@ -0,0 +1,77 @@
+// A naive implementation of an immediate mode gui.
+
+#ifndef ED_UI_INCLUDED
+#define ED_UI_INCLUDED
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include "string.h"
+
+typedef enum {
+    UI_AXIS_HORIZONTAL,
+    UI_AXIS_VERTICAL,
+} ui_axis;
+
+typedef enum {
+    UI_SEMANTIC_SIZE_FIT_TEXT,
+    UI_SEMANTIC_SIZE_CHILDREN_SUM,
+    UI_SEMANTIC_SIZE_FILL,
+    UI_SEMANTIC_SIZE_EXACT,
+    UI_SEMANTIC_SIZE_PERCENT_OF_PARENT,
+} ui_semantic_size_t;
+
+typedef struct {
+    ui_semantic_size_t type;
+    union {
+        uint32_t integer;
+    };
+} ui_semantic_size;
+
+typedef struct {
+    ui_axis axis;
+    ui_semantic_size semantic_size[2];
+    uint32_t computed_size[2];
+    uint32_t computed_pos[2]; 
+} ui_size;
+
+// UI Element data persisted across frames
+typedef struct {
+    string label;
+    ui_size size;
+    size_t last_instantiated_index;
+} ui_element_cache_data;
+
+typedef enum {
+    UI_FLAG_CLICKABLE         =  0b000000001,
+    UI_FLAG_HOVERABLE         =  0b000000010,
+    UI_FLAG_SCROLLABLE        =  0b000000100,
+    UI_FLAG_DRAW_TEXT         =  0b000001000,
+    UI_FLAG_DRAW_BORDER       =  0b000010000,
+    UI_FLAG_DRAW_BACKGROUND   =  0b000100000,
+    UI_FLAG_ROUNDED_BORDER    =  0b001000000,
+    UI_FLAG_FLOATING          =  0b010000000,
+    UI_FLAG_CUSTOM_DRAW_FUNC  =  0b100000000,
+} ui_flags;
+
+// Ephemeral frame only UI Element data
+typedef struct {
+    size_t index;
+    string key;
+    string label;
+
+    ui_size size;
+    ui_flags flags;
+
+    // optional types
+    size_t first;
+    size_t last;
+    size_t next;
+    size_t prev;
+    size_t parent;
+} ui_element_frame_data;
+
+#endif
+
+#ifdef ED_UI_IMPLEMENTATION
+#endif