diff --git a/src/design-tokens.cg b/src/design-tokens.cg
new file mode 100644
index 0000000..ea0b546
--- /dev/null
+++ b/src/design-tokens.cg
@@ -0,0 +1,38 @@
+colors = {
+  primary = "#0066cc",
+  primaryDark = "#0052a3",
+  danger = "#dc3545",
+  success = "#28a745",
+  bg = "#ffffff",
+  bgGray = "#f8f9fa",
+  text = "#212529",
+  textLight = "#6c757d",
+  border = "#dee2e6"
+};
+
+spacing = {
+  xs = 4,
+  sm = 8,
+  md = 16,
+  lg = 32,
+  xl = 64
+};
+
+primaryStyle = {
+  bg = colors.primary,
+  fg = colors.bg,
+  px = spacing.md,
+  py = spacing.sm
+};
+
+dangerStyle = {
+  bg = colors.danger,
+  fg = colors.bg,
+  px = spacing.md,
+  py = spacing.sm
+};
+
+theme = {
+  colors = colors,
+  spacing = spacing
+};
diff --git a/src/main.ts b/src/main.ts
index 4a76306..4901bd8 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -5,18 +5,21 @@ import { Parser } from './parser'
 import { runApp } from './runtime';
 import { builtins } from './builtins';
 
-import counterApp from './counter.cg?raw';
 import stdlibCode from './stdlib.cg?raw';
+import designTokensCode from './design-tokens.cg?raw';
 import uiComponentsCode from './ui-components.cg?raw';
+
 import textInputCode from './textinput-test.cg?raw';
 import testCode from './test.cg?raw';
+import counterApp from './counter.cg?raw';
 
 const canvas = document.createElement('canvas');
 canvas.width = 800;
 canvas.height = 600;
+canvas.style.border = "1px solid #000";
 document.body.appendChild(canvas);
 
-const cgCode = stdlibCode + '\n' + uiComponentsCode + '\n' + textInputCode;
+const cgCode = stdlibCode + '\n' + designTokensCode + '\n' + uiComponentsCode + '\n' + textInputCode;
 
 const tokens = tokenize(cgCode);
 const parser = new Parser(tokens);
diff --git a/src/runtime.ts b/src/runtime.ts
index 42a5613..8750c28 100644
--- a/src/runtime.ts
+++ b/src/runtime.ts
@@ -16,7 +16,7 @@ export function runApp(app: App, canvas: HTMLCanvasElement) {
         if (app.view.kind !== 'closure')
             throw new Error('view must be a function');
 
-        const viewport = {
+        const viewport: Value = {
             kind: 'record',
             fields: {
                 width: { kind: 'int', value: canvas.width },
@@ -61,13 +61,9 @@ export function runApp(app: App, canvas: HTMLCanvasElement) {
             return;
         }
 
-        const eventName = hitTest(x, y);
-        if (eventName) {
-            const event: Value = {
-                kind: 'constructor',
-                name: eventName,
-                args: []
-            }
+
+        const event = hitTest(x, y);
+        if (event) {
             handleEvent(event);
         }
     });
diff --git a/src/textinput-test.cg b/src/textinput-test.cg
index 58ef6be..ddb268e 100644
--- a/src/textinput-test.cg
+++ b/src/textinput-test.cg
@@ -2,17 +2,22 @@ init = { text = "" };
 
 update = state event \ event
   | UpdateText newText \ state.{ text = newText }
-  | Submit _ \ state.{ text = "" };
-  # | _ \ state;
+  | Submit _ \ state.{ text = "" }
+  | Go \ state.{ text = "" };
 
 view = state viewport \
   Column {
     gap = 20,
     children = [
+      Text {
+          content = "window: " & str(viewport.width) & " x " & str(viewport.height),
+          x = 0,
+          y = 20
+      },
       Text { content = "You typed: " & state.text, x = 0, y = 20 },
       Stack {
         children = [
-          Rect { w = 300, h = 40, color = "white" },
+          Rect { w = viewport.width, h = 40, color = "blue" },
           TextInput {
             value = state.text,
             placeholder = "Type something...",
@@ -24,9 +29,9 @@ view = state viewport \
             onInput = UpdateText,
             onSubmit = Submit
           }
-          # button ({ label = "Go", event = Go })
         ]
-      }
+      },
+      button { label = "Go", event = Go, theme = theme }
     ]
   };
 
diff --git a/src/types.ts b/src/types.ts
index d622b97..3b467c6 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -51,7 +51,7 @@ export type UIValue =
     | { kind: 'text', content: string, x: number, y: number }
     | { kind: 'row', children: UIValue[], gap: number }
     | { kind: 'column', children: UIValue[], gap: number }
-    | { kind: 'clickable', child: UIValue, event: string }
+    | { kind: 'clickable', child: UIValue, event: Value }
     | { kind: 'padding', child: UIValue, amount: number }
     | { kind: 'stack', children: UIValue[] }
     | { kind: 'text-input', value: string, placeholder: string, x: number, y: number, w: number, h: number, focused: boolean, onInput: Value, onSubmit: Value }
diff --git a/src/ui-components.cg b/src/ui-components.cg
index 1874853..d1a4616 100644
--- a/src/ui-components.cg
+++ b/src/ui-components.cg
@@ -1,10 +1,11 @@
+# button : Record -> UI
 button = config \
     Clickable {
         event = config.event,
         child = Stack {
             children = [
-                Rect { w = 100, h = 40, color = "blue" },
-                Text { content = config.label, x = 10, y = 25}
+                Rect { w = 100, h = 40, color = config.theme.colors.primary },
+                Text { content = config.label, x = 10, y = 25, color = config.theme.colors.bg }
             ]
         }
     };
diff --git a/src/ui.ts b/src/ui.ts
index 114ba66..c7f98d0 100644
--- a/src/ui.ts
+++ b/src/ui.ts
@@ -5,7 +5,7 @@ type ClickRegion = {
     y: number;
     width: number;
     height: number;
-    event: string;
+    event: Value;
 };
 
 type TextInputRegion = {
@@ -171,14 +171,12 @@ function measure(ui: UIValue): { width: number, height: number } {
         case 'text-input':
             return { width: ui.w, height: ui.h };
     }
-
-    // return { width: 0, height: 0 };
 }
 
-export function hitTest(x: number, y: number): string | null {
+export function hitTest(x: number, y: number): Value | null {
     for (const region of clickRegions) {
         if (x >= region.x && x < region.x + region.width &&
-           x >= region.y && y < region.y + region.height) {
+           y >= region.y && y < region.y + region.height) {
             return region.event;
         }
     }
diff --git a/src/valueToUI.ts b/src/valueToUI.ts
index 24e7b13..cfc2ef4 100644
--- a/src/valueToUI.ts
+++ b/src/valueToUI.ts
@@ -57,10 +57,10 @@ export function valueToUI(value: Value): UIValue {
             const child = fields.child;
             const event = fields.event;
 
-            if (event.kind !== 'string')
-                throw new Error('Invalid Clickable fields');
+            if (event.kind !== 'constructor')
+                throw new Error('Clickable event must be a constructor');
 
-            return { kind: 'clickable', event: event.value, child: valueToUI(child) };
+            return { kind: 'clickable', event: event, child: valueToUI(child) };
         }
 
         case 'Padding': {