diff --git a/src/cg/10-os.cg b/src/cg/10-os.cg
index 835d281..5d5b33a 100644
--- a/src/cg/10-os.cg
+++ b/src/cg/10-os.cg
@@ -2,68 +2,107 @@ osState = {
   palette = {
     visible = True
   },
-  inspector = {
-    visible = False,
-    name = ""
-  }
+  windows = [],
+  wm = {
+    focusedIndex = 0,
+    scrollOffset = 0
+  },
+  nextId = 0
 };
 
-run = cmd \
-  _ = debug "run" cmd;
-  result = eval cmd;
-  _ = debug "result" result;
-  result
-    | Defined name \ debug "defined" name
-    | Value v \ debug "result" v
-    | Err msg \ debug "error" msg
-    | _ \ noOp;
-
-onSelect = item \
-  # for now, if it matches a store item, inspect it
-  # if not, eval it
-  res = storeSearch item;
-  zeroth = nth 0 res;
-  (and (len res > 0) (nth 0 res == Some item))
-  | True \ inspect item
-  | _ \ run item;
-
-inspect = item \
+openWindow = title content \
+  id = osState.nextId;
   batch [
-    osState.palette.visible := False,
-    osState.inspector.visible := True,
-    osState.inspector.name := item
+    osState.nextId := id + 1,
+    osState.windows := osState.windows & [{ id = id, title = title, content = content, width = 400 }],
+    osState.palette.visible := False
   ];
 
-init = {};
+closeFocused = _ \
+  i = osState.wm.focusedIndex;
+  batch [
+    osState.windows := (take i osState.windows) & (drop (i + 1) osState.windows),
+    osState.wm.focusedIndex := max 0 (osState.wm.focusedIndex - 1)
+  ];
 
-update = state event \ event
-  | Key { key = "p", meta = True } \
-    { state = state, emit = [osState.palette.visible := not (osState.palette.visible)] }
-  | _ \ { state = state, emit = [] };
+onSelect = input \
+  result = eval input;
+  result
+  | Value v \ openWindow input (ui.text { content = show v, color = "white" })
+  | Defined name \ noOp
+  | Err msg \ openWindow "Error" (ui.text { content = msg, color = "red" });
 
-view = state viewport \
+renderWindow = window isActive \
+  _ = debug "renderWindow" window.title;
+  titleBarHeight = 30;
   ui.stack {
     children = [
-      ui.rect { w = viewport.width, h = viewport.height, color = "#012" },
+      # background
+      ui.rect { w = window.width, h = viewport.height, color = (isActive | True \ "#0a2a3a" | False \ "#061820")},
 
-      osState.inspector.visible
-      | True \ inspector {
-          name = osState.inspector.name,
-          viewport = viewport,
+      # title bar
+      ui.positioned {
+        x = 0, y = 0,
+        child = ui.stack {
+          children = [
+            ui.rect { w = window.width, h = titleBarHeight, color = (isActive | True \ "#a15f80" | False \ "#0f3348") },
+            ui.positioned { x = 8, y = 8, child = ui.text { content = window.title, color = "white" } },
+          ]
         }
-      | False \ empty,
+      },
 
-      # keep palette at the end so it's on top
-      osState.palette.visible
-      | True \ palette {
-          # state = osState.palette,
-          # query = osState.palette.query,
-          search = storeSearch,
-          onSelect = onSelect,
-          viewport = viewport,
+      # content
+      ui.positioned {
+        x = 0, y = titleBarHeight,
+        child = ui.clip {
+          w = window.width,
+          h = viewport.height - titleBarHeight,
+          child = window.content
         }
-      | False \ empty,
+      }
     ]
   };
 
-os = { init = init, update = update, view = view }
+renderWindows = _ \
+  windows = osState.windows;
+  focused = osState.wm.focusedIndex;
+  ui.row {
+    gap = 1,
+    children = mapWithIndex (w i \ renderWindow w (i == focused)) windows
+  };
+
+os = ui.stateful {
+  key = "os",
+  autoFocus = True,
+
+  init = {},
+
+  update = state event \ event
+    | Key { key = "p", meta = True } \
+      { state = state, emit = [osState.palette.visible := not (osState.palette.visible)] }
+    | Key { key = "ArrowLeft", meta = True } \
+      { state = state, emit = [osState.wm.focusedIndex := max 0 (osState.wm.focusedIndex - 1)] }
+    | Key { key = "ArrowRight", meta = True } \
+      { state = state, emit = [osState.wm.focusedIndex := min (len osState.windows - 1) (osState.wm.focusedIndex + 1)] }
+    | Key { key = "d", meta = True } \
+      { state = state, emit = [closeFocused 0] }
+    | _ \ _ = debug "key" []; { state = state, emit = [] },
+
+  view = state \
+    ui.stack {
+      children = [
+        ui.rect { w = viewport.width, h = viewport.height, color = "#012" },
+
+        renderWindows 0,
+
+        # keep palette at the end so it's on top
+        osState.palette.visible
+        | True \ palette {
+            search = storeSearch,
+            onSelect = onSelect,
+            viewport = viewport,
+          }
+        | False \ empty,
+      ]
+    }
+  };
diff --git a/src/compiler.ts b/src/compiler.ts
index 47e09b4..dc7bc02 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -1,13 +1,15 @@
 import type { AST, Pattern, Definition } from './ast';
-import { _rt, store } from './runtime-js';
+import { store } from './runtime-js';
 
 let matchCounter = 0;
 
 export const definitions: Map<string, AST> = new Map();
 export const dependencies: Map<string, Set<string>> = new Map();
 export const dependents: Map<string, Set<string>> = new Map();
+export const astRegistry = new Map<number, AST>();
+let astIdCounter = 0;
 
-export function compile(ast: AST, useStore = true, bound = new Set<string>()): string {
+export function compile(ast: AST, useStore = true, bound = new Set<string>(), topLevel = new Set<string>()): string {
     switch (ast.kind) {
         case 'literal':
             if (ast.value.kind === 'string')
@@ -18,61 +20,62 @@ export function compile(ast: AST, useStore = true, bound = new Set<string>()): s
 
         case 'variable': {
             if (bound.has(ast.name)) {
-            return sanitizeName(ast.name);
+                return sanitizeName(ast.name);
             }
-            return sanitize(ast.name, useStore);
+            return sanitize(ast.name, useStore, topLevel);
         }
 
         case 'lambda': {
             const newBound = new Set([...bound, ...ast.params]);
             const params = ast.params.map(sanitizeName).join(') => (');
-            return `Object.assign((${params}) => ${compile(ast.body, useStore, newBound)}, { _ast: (${JSON.stringify(ast)}) })`;
+            const id = astIdCounter++;
+            return `Object.assign((${params}) => ${compile(ast.body, useStore, newBound, topLevel)}, { _astId: (${id}) })`;
         }
 
         case 'apply':
             // Constructor
             if (ast.func.kind === 'constructor') {
                 const ctorName = ast.func.name;
-                const arg = compile(ast.args[0], useStore, bound);
+                const arg = compile(ast.args[0], useStore, bound, topLevel);
                 return `((_a) => _a && typeof _a === 'object' && !Array.isArray(_a) && !_a._tag
                          ? { _tag: "${ctorName}", ..._a }
                          : { _tag: "${ctorName}", _0: _a })(${arg})`;
             }
 
-            const args = ast.args.map(a => compile(a, useStore, bound)).join(')(');
-            return `${compile(ast.func, useStore, bound)}(${args})`;
+            const args = ast.args.map(a => compile(a, useStore, bound, topLevel)).join(')(');
+            return `${compile(ast.func, useStore, bound, topLevel)}(${args})`;
 
         case 'record': {
             const parts = ast.entries.map(entry =>
                                          entry.kind === 'spread'
-                                         ? `...${compile(entry.expr, useStore, bound)}`
-                                         : `${sanitizeName(entry.key)}: ${compile(entry.value, useStore, bound)}`
+                                         ? `...${compile(entry.expr, useStore, bound, topLevel)}`
+                                         : `${sanitizeName(entry.key)}: ${compile(entry.value, useStore, bound, topLevel)}`
                                          )
             return `({${parts.join(', ')}})`;
         }
 
         case 'list': {
             const elements = ast.elements.map(e =>
-                'spread' in e ? `...${compile(e.spread, useStore, bound)}` : compile(e, useStore, bound)
+                'spread' in e ? `...${compile(e.spread, useStore, bound, topLevel)}` : compile(e, useStore, bound, topLevel)
             );
             return `[${elements.join(', ')}]`;
         }
 
         case 'record-access':
-            return `${compile(ast.record, useStore, bound)}.${sanitizeName(ast.field)}`;
+            return `${compile(ast.record, useStore, bound, topLevel)}.${sanitizeName(ast.field)}`;
 
         case 'record-update':
             const updates = Object.entries(ast.updates)
-                .map(([k, v]) => `${sanitizeName(k)}: ${compile(v, useStore, bound)}`);
-            return `({...${compile(ast.record, useStore, bound)}, ${updates.join(', ')}})`;
+                .map(([k, v]) => `${sanitizeName(k)}: ${compile(v, useStore, bound, topLevel)}`);
+            return `({...${compile(ast.record, useStore, bound, topLevel)}, ${updates.join(', ')}})`;
 
         case 'let':
             const newBound = new Set([...bound, ast.name]);
             return `((${sanitizeName(ast.name)}) =>
-                     ${compile(ast.body, useStore, newBound)})(${compile(ast.value, useStore, bound)})`;
+                     ${compile(ast.body, useStore, newBound, topLevel)})(${compile(ast.value, useStore, bound, topLevel)})`;
 
         case 'match':
-            return compileMatch(ast, useStore, bound);
+            return compileMatch(ast, useStore, bound, topLevel);
 
         case 'constructor':
             return `({ _tag: "${ast.name}" })`;
@@ -85,10 +88,15 @@ export function compile(ast: AST, useStore = true, bound = new Set<string>()): s
         case 'rebind': {
             const rootName = getRootName(ast.target);
             const path = getPath(ast.target);
-            const value = compile(ast.value, useStore, bound);
+            const value = compile(ast.value, useStore, bound, topLevel);
 
             if (!rootName) throw new Error('Rebind target must be a variable');
 
+            if (bound.has(rootName)) {
+                const target = compile(ast.target, useStore, bound, topLevel);
+                return `(() => { ${target} = ${value}; return { _tag: "NoOp" }; })()`;
+            }
+
             if (path.length === 0) {
                 return `({ _tag: "Rebind", _0: "${rootName}", _1: ${value} })`;
             } else {
@@ -102,23 +110,9 @@ export function compile(ast: AST, useStore = true, bound = new Set<string>()): s
     }
 }
 
-function sanitize(name: string, useStore = true): string {
-    const ops: Record<string, string> = {
-        'add': '_rt.add', 'sub': '_rt.sub', 'mul': '_rt.mul', 'div': '_rt.div',
-        'mod': '_rt.mod', 'pow': '_rt.pow',
-        'eq': '_rt.eq', 'gt': '_rt.gt', 'lt': '_rt.lt', 'gte': '_rt.gte', 'lte': '_rt.lte',
-        'cat': '_rt.cat', 'max': '_rt.max', 'min': '_rt.min',
-    };
-
-    if (ops[name]) return ops[name];
-
-    const natives = ['eval', 'measure', 'measureText', 'storeSearch', 'getSource', 'debug', 'nth', 'len', 'slice', 'join', 'chars', 'split', 'str', 'redefine', 'undefine', 'batch', 'noOp', 'focus', 'ui'];
-    if (natives.includes(name)) return `_rt.${name}`;
-
-    if (useStore) {
-        return `store.${sanitizeName(name)}`;
-    }
-    return sanitizeName(name);
+function sanitize(name: string, useStore = true, topLevel: Set<string>): string {
+    if (!useStore && topLevel.has(name)) return sanitizeName(name);
+    return `store[${JSON.stringify(name)}]`
 }
 
 function sanitizeName(name: string): string {
@@ -135,8 +129,8 @@ function sanitizeName(name: string): string {
     return name.replace(/-/g, '_');
 }
 
-function compileMatch(ast: AST & { kind: 'match'}, useStore = true, bound = new Set<string>()): string {
-    const expr = compile(ast.expr, useStore, bound);
+function compileMatch(ast: AST & { kind: 'match'}, useStore = true, bound = new Set<string>(), topLevel = new Set<string>()): string {
+    const expr = compile(ast.expr, useStore, bound, topLevel);
     const tmpVar = `_m${matchCounter++}`;
 
     let code = `((${tmpVar}) => { `;
@@ -149,7 +143,7 @@ function compileMatch(ast: AST & { kind: 'match'}, useStore = true, bound = new
         if (bindings.length > 0) {
             code += `const ${bindings.join(', ')}; `;
         }
-        code += `return ${compile(c.result, useStore, newBound)}; }`;
+        code += `return ${compile(c.result, useStore, newBound, topLevel)}; }`;
     }
 
     code += `console.error("No match for:", ${tmpVar}); throw new Error("No match"); })(${expr})`;
@@ -245,11 +239,11 @@ export function compileAndRun(defs: Definition[]) {
     }
 
     for (const def of defs) {
-        const compiled = `const ${sanitizeName(def.name)} = ${compile(def.body, false)};`;
+        const compiled = `const ${sanitizeName(def.name)} = ${compile(def.body, false, new Set(), topLevel)};`;
         compiledDefs.push(compiled);
 
         try {
-            new Function('_rt', compiled);
+            new Function('store', compiled);
         } catch (e) {
             console.error(`=== BROKEN: ${def.name} ===`);
             console.error(compiled);
@@ -263,8 +257,8 @@ export function compileAndRun(defs: Definition[]) {
     const code = `${compiledDefs.join('\n')}
 return { ${defNames}, __result: ${sanitizeName(lastName)} };`;
 
-    const fn = new Function('_rt', 'store', code);
-    const allDefs = fn(_rt, store);
+    const fn = new Function('store', code);
+    const allDefs = fn(store);
 
     // Populate store
     for (const [name, value] of Object.entries(allDefs)) {
@@ -397,8 +391,8 @@ export function recompile(name: string, newAst: AST) {
         const ast = definitions.get(defName)!;
         const compiled = compile(ast);
 
-        const fn = new Function('_rt', 'store', `return ${compiled}`);
-        store[defName] = fn(_rt, store);
+        const fn = new Function('store', `return ${compiled}`);
+        store[defName] = fn(store);
     }
 }
 
diff --git a/src/main.ts b/src/main.ts
index 1c77c51..d01c35f 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2,7 +2,7 @@ import { compileAndRun } from './compiler'
 import { tokenize } from './lexer'
 import { Parser } from './parser'
 import { runAppCompiled } from './runtime-compiled'
-import { _rt, loadDefinitions, saveDefinitions } from './runtime-js'
+import { _rt, store, loadDefinitions, saveDefinitions } from './runtime-js'
 
 const modules = import.meta.glob('./cg/*.cg', { query: 'raw', import: 'default', eager: true });
 const cgCode = Object.keys(modules)
@@ -13,20 +13,22 @@ const cgCode = Object.keys(modules)
 const canvas = document.createElement('canvas') as HTMLCanvasElement;
 document.body.appendChild(canvas);
 
+// Populate store with natives
+for (const [name, value] of Object.entries(_rt)) {
+    store[name] = value;
+}
+
+store.viewport = { width: window.innerWidth, height: window.innerHeight };
+
 try {
     const tokens = tokenize(cgCode);
     const parser = new Parser(tokens, cgCode);
     const defs = parser.parse();
     loadDefinitions();
-    const os = compileAndRun(defs);
+    compileAndRun(defs);
     saveDefinitions();
 
-    runAppCompiled(
-        { init: os.init, update: os.update, view: os.view },
-        canvas,
-        _rt
-    );
-
+    runAppCompiled(canvas, store);
 } catch(error) {
     console.error(error);
 }
diff --git a/src/runtime-compiled.ts b/src/runtime-compiled.ts
index 0761bfb..7491402 100644
--- a/src/runtime-compiled.ts
+++ b/src/runtime-compiled.ts
@@ -2,20 +2,13 @@ import { render, hitTest } from './ui';
 
 type UIValue = any;
 
-type App = {
-    init: any;
-    update: (state: any) => (event: any) => any;
-    view: (state: any) => (viewport: any) => any;
-}
-
 type ComponentInstance = {
     state: any;
     update: (state: any) => (event: any) => any;
     view: (state: any) => any;
 };
 
-export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
-    let state = app.init;
+export function runAppCompiled(canvas: HTMLCanvasElement, store: any) {
     const componentInstances = new Map<string, ComponentInstance>();
     let focusedComponentKey: string | null = null;
 
@@ -132,13 +125,10 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
     }
 
     function rerender() {
-        const viewport = { width: window.innerWidth, height: window.innerHeight };
         const renderedKeys = new Set<string>();
 
         try {
-            const uiValue = app.view(state)(viewport);
-            const ui = uiValue;
-            const expandedUI = expandStateful(ui, [], renderedKeys);
+            const expandedUI = expandStateful(store.os, [], renderedKeys);
 
             // clean up unrendered instances
             for (const key of componentInstances.keys()) {
@@ -148,7 +138,16 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
             }
 
             if (focusedComponentKey && !renderedKeys.has(focusedComponentKey)) {
+                const parts = focusedComponentKey.split('.');
                 focusedComponentKey = null;
+                while (parts.length > 0) {
+                    parts.pop();
+                    const ancestor = parts.join('.');
+                    if (ancestor && renderedKeys.has(ancestor)) {
+                        focusedComponentKey = ancestor;
+                        break;
+                    }
+                }
             }
 
             render(expandedUI, canvas);
@@ -182,7 +181,7 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
         }
 
         if (event._tag === 'Rebind') {
-            rt.rebind(event._0, event._1, event._2);
+            store.rebind(event._0, event._1, event._2);
             return;
         }
 
@@ -193,14 +192,6 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
 
         if (event._tag === 'NoOp')
             return;
-
-        const result = app.update(state)(event);
-        state = result.state;
-        if (result.emit && Array.isArray(result.emit)) {
-            for (const e of result.emit) {
-                handleEvent(e);
-            }
-        }
     }
 
     canvas.addEventListener('click', (e) => {
@@ -251,9 +242,6 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
             }
         }
 
-        // OS root
-        handleEvent(event);
-
         e.preventDefault();
         rerender();
     });
@@ -263,6 +251,7 @@ export function runAppCompiled(app: App, canvas: HTMLCanvasElement, rt: any) {
         cancelAnimationFrame(resizeRAF);
         resizeRAF = requestAnimationFrame(() => {
             setupCanvas();
+            store.viewport = { width: window.innerWidth, height: window.innerHeight };
             rerender();
         });
     });
diff --git a/src/runtime-js.ts b/src/runtime-js.ts
index 614e723..925d5b9 100644
--- a/src/runtime-js.ts
+++ b/src/runtime-js.ts
@@ -1,6 +1,6 @@
 import { tokenize } from './lexer'
 import { Parser } from './parser'
-import { compile, recompile, definitions, freeVars, dependencies, dependents } from './compiler'
+import { compile, recompile, definitions, freeVars, dependencies, dependents, astRegistry } from './compiler'
 import { prettyPrint } from './ast'
 import type { AST } from './ast'
 import { measure } from './ui';
@@ -61,7 +61,21 @@ export const _rt = {
         ? { _tag: 'Some', _0: xs[i] }
         : { _tag: 'None' },
     len: (xs: any[] | string) => xs.length,
-    str: (x: any) => String(x),
+    // str: (x: any) => String(x),
+    show: (value: any): string => {
+        if (value === null || value === undefined) return "None";
+        if (typeof value === 'string') return value;
+        if (typeof value === 'number') return String(value);
+        if (typeof value === 'boolean') return value ? "True" : "False";
+        if (value._tag) return value._0 !== undefined ? `${value._tag} ${_rt.show(value._0)}` : value._tag;
+        if (Array.isArray(value)) return `[${value.map(_rt.show).join(", ")}]`;
+        if (typeof value === 'function') return "<function>";
+        if (typeof value === 'object') {
+            const entries = Object.entries(value).map(([k, v]) => `${k} = ${_rt.show(v)}`);
+            return `{ ${entries.join(", ")} }`;
+        }
+        return String(value);
+    },
     chars: (s: string) => s.split(''),
     join: (delim: string) => (xs: string[]) => xs.join(delim),
     split: (delim: string) => (xs: string) => xs.split(delim),
@@ -183,7 +197,7 @@ export function loadDefinitions() {
 
     try {
         const saved = JSON.parse(data);
-        for (const [name, source] of Object.entries(saved)) {
+        for (const [_, source] of Object.entries(saved)) {
             const tokens = tokenize(source as string);
             const parser = new Parser(tokens, source as string);
             const defs = parser.parse();
@@ -245,11 +259,11 @@ function valueToAst(value: any): AST {
 
     // Functions
     if (typeof value === 'function') {
-        if (value._ast) {
-            return value._ast;
+        if (value._astId !== undefined) {
+            return astRegistry.get(value._astId)!;
         }
 
-        throw new Error('Cannot serialize function without _ast');
+        throw new Error('Cannot serialize function without _astId');
     }
 
     throw new Error(`Cannot convert to AST: ${typeof value}`);