diff --git a/src/index.css b/src/index.css
new file mode 100644
index 0000000..cf391e9
--- /dev/null
+++ b/src/index.css
@@ -0,0 +1,26 @@
+/* Global page styles. Phase-2 minimum-viable tonal coherence — body bg
+ * matches the Phaser canvas backgroundColor (#1a1a1a) and the BeginScreen
+ * overlay so there is no white halo around the dark canvas at any moment.
+ *
+ * Phase 3 (Watercolor & Cello) layers a painted treatment on top of this
+ * base; this file establishes the foundation that the painted treatment
+ * layers over.
+ *
+ * Per CLAUDE.md tone constraint and anti-FOMO doctrine — calm, contemplative,
+ * no animation, no urgency.
+ */
+
+html, body {
+  margin: 0;
+  padding: 0;
+  min-height: 100vh;
+  background: #1a1a1a;
+  color: #e8e0d0;
+  font-family: serif;
+}
+
+#game-container {
+  display: flex;
+  justify-content: center;
+  align-items: center;
+}
diff --git a/src/index.css.test.ts b/src/index.css.test.ts
new file mode 100644
index 0000000..405160c
--- /dev/null
+++ b/src/index.css.test.ts
@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+/**
+ * G1 (gap closure 02-06) — assert src/index.css contains the load-bearing
+ * tonal-coherence rules. We test by file-read because Vitest jsdom does
+ * not bundle CSS imports; the e2e (tests/e2e/season1-loop.spec.ts) is the
+ * end-to-end proof that the bundled CSS actually applies in a real browser.
+ */
+describe('src/index.css (Plan 02-06 G1 closure)', () => {
+  const cssPath = join(__dirname, 'index.css');
+  const css = readFileSync(cssPath, 'utf8');
+
+  it('sets body background to #1a1a1a (matches Phaser canvas)', () => {
+    expect(css).toMatch(/background:\s*#1a1a1a/);
+  });
+
+  it('sets body color to #e8e0d0 (matches BeginScreen palette)', () => {
+    expect(css).toMatch(/color:\s*#e8e0d0/);
+  });
+
+  it('zeroes body margin (kills browser default white halo)', () => {
+    expect(css).toMatch(/margin:\s*0/);
+  });
+
+  it('sets body min-height to 100vh (dark bg fills viewport)', () => {
+    expect(css).toMatch(/min-height:\s*100vh/);
+  });
+
+  it('uses serif font-family (matches BeginScreen)', () => {
+    expect(css).toMatch(/font-family:\s*serif/);
+  });
+
+  it('main.tsx imports the CSS', () => {
+    const mainPath = join(__dirname, 'main.tsx');
+    const main = readFileSync(mainPath, 'utf8');
+    expect(main).toMatch(/import\s+['"]\.\/index\.css['"]/);
+  });
+});
diff --git a/src/main.tsx b/src/main.tsx
index b04c04e..db7ea87 100644
--- a/src/main.tsx
+++ b/src/main.tsx
@@ -1,6 +1,7 @@
 import { StrictMode } from 'react';
 import { createRoot } from 'react-dom/client';
 import App from './App.tsx';
+import './index.css'; // Plan 02-06 G1 — global page styles (body bg, font, margin)
 
 const rootEl = document.getElementById('root');
 if (!rootEl) {