Add UX experiments page

diff --git a/ui/src/plugins/dev.perfetto.UxPlayground/index.ts b/ui/src/plugins/dev.perfetto.UxPlayground/index.ts
new file mode 100644
index 0000000..471b0dc
--- /dev/null
+++ b/ui/src/plugins/dev.perfetto.UxPlayground/index.ts

@@ -0,0 +1,39 @@
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import './styles.scss';
+import m from 'mithril';
+import type {App} from '../../public/app';
+import type {PerfettoPlugin} from '../../public/plugin';
+import {UxPlaygroundPage} from './ux_playground_page';
+
+// A scratch page for experimenting with UX designs. Add new experiments in
+// ux_playground_page.ts. Reachable at #!/ux.
+export default class implements PerfettoPlugin {
+  static readonly id = 'dev.perfetto.UxPlayground';
+
+  static onActivate(app: App): void {
+    app.pages.registerPage({
+      route: '/ux',
+      render: (subpage) => m(UxPlaygroundPage, {app, subpage}),
+    });
+    app.sidebar.addMenuItem({
+      section: 'settings',
+      text: 'UX Playground',
+      href: '#!/ux',
+      icon: 'science',
+      sortOrder: 99,
+    });
+  }
+}

diff --git a/ui/src/plugins/dev.perfetto.UxPlayground/styles.scss b/ui/src/plugins/dev.perfetto.UxPlayground/styles.scss
new file mode 100644
index 0000000..d11b2c5
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+++ b/ui/src/plugins/dev.perfetto.UxPlayground/styles.scss

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+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+.pf-ux-playground {
+  height: 100%;
+  overflow: auto;
+  padding: 24px;
+}

diff --git a/ui/src/plugins/dev.perfetto.UxPlayground/ux_playground_page.ts b/ui/src/plugins/dev.perfetto.UxPlayground/ux_playground_page.ts
new file mode 100644
index 0000000..871e0c7
--- /dev/null
+++ b/ui/src/plugins/dev.perfetto.UxPlayground/ux_playground_page.ts

@@ -0,0 +1,30 @@
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import m from 'mithril';
+import type {App} from '../../public/app';
+
+export interface UxPlaygroundPageAttrs {
+  readonly app: App;
+  readonly subpage?: string;
+}
+
+// Blank scratch page for experimenting with UX designs.
+export class UxPlaygroundPage
+  implements m.ClassComponent<UxPlaygroundPageAttrs>
+{
+  view() {
+    return m('.pf-ux-playground');
+  }
+}