diff --git a/.prettierignore b/.prettierignore
index 1916473..653166b 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -10,5 +10,10 @@ pnpm-lock.yaml
 *.docx
 *.pdf
 
+# Playwright artifacts
+**/test-results/
+**/playwright-report/
+**/playwright/.cache/
+
 # User-authored project doc — preserve exact formatting
 CLAUDE.md
diff --git a/apps/web/.gitignore b/apps/web/.gitignore
index 2472ac6..da260b4 100644
--- a/apps/web/.gitignore
+++ b/apps/web/.gitignore
@@ -3,3 +3,7 @@ out/
 next-env.d.ts.bak
 .vercel/
 *.tsbuildinfo
+test-results/
+playwright-report/
+playwright/.cache/
+blob-report/
diff --git a/apps/web/e2e/home.spec.ts b/apps/web/e2e/home.spec.ts
new file mode 100644
index 0000000..0ba446b
--- /dev/null
+++ b/apps/web/e2e/home.spec.ts
@@ -0,0 +1,11 @@
+import { expect, test } from '@playwright/test';
+
+test('home page renders Italian copy and CTAs', async ({ page }) => {
+  await page.goto('/');
+
+  await expect(page).toHaveTitle(/KetoPath/);
+  await expect(page.getByRole('heading', { name: 'KetoPath' })).toBeVisible();
+  await expect(page.getByRole('button', { name: 'Inizia gratis' })).toBeVisible();
+  await expect(page.getByRole('button', { name: 'Scopri come funziona' })).toBeVisible();
+  await expect(page.getByText(/non sostituiscono il parere di un medico/)).toBeVisible();
+});
diff --git a/apps/web/package.json b/apps/web/package.json
index d336931..b0a742b 100644
--- a/apps/web/package.json
+++ b/apps/web/package.json
@@ -7,7 +7,8 @@
     "build": "next build",
     "start": "next start --port 3000",
     "typecheck": "tsc --noEmit",
-    "lint": "next lint --max-warnings=0"
+    "lint": "next lint --max-warnings=0",
+    "test:e2e": "playwright test"
   },
   "dependencies": {
     "@ketopath/shared": "workspace:*",
@@ -26,6 +27,7 @@
     "autoprefixer": "^10.4.19",
     "eslint-config-next": "^14.2.5",
     "postcss": "^8.4.39",
-    "tailwindcss": "^3.4.4"
+    "tailwindcss": "^3.4.4",
+    "@playwright/test": "^1.45.3"
   }
 }
diff --git a/apps/web/playwright.config.ts b/apps/web/playwright.config.ts
new file mode 100644
index 0000000..10c1e33
--- /dev/null
+++ b/apps/web/playwright.config.ts
@@ -0,0 +1,24 @@
+import { defineConfig, devices } from '@playwright/test';
+
+const PORT = 3000;
+const baseURL = `http://localhost:${PORT}`;
+
+export default defineConfig({
+  testDir: './e2e',
+  fullyParallel: true,
+  forbidOnly: Boolean(process.env.CI),
+  retries: process.env.CI ? 2 : 0,
+  workers: process.env.CI ? 1 : undefined,
+  reporter: process.env.CI ? 'github' : 'list',
+  use: {
+    baseURL,
+    trace: 'on-first-retry',
+  },
+  projects: [{ name: 'chromium', use: { ...devices['Desktop Chrome'] } }],
+  webServer: {
+    command: 'pnpm dev',
+    url: baseURL,
+    reuseExistingServer: !process.env.CI,
+    timeout: 120_000,
+  },
+});
diff --git a/package.json b/package.json
index c009aa6..8e91b24 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,9 @@
     "format": "prettier --write .",
     "format:check": "prettier --check .",
     "typecheck": "tsc -b",
-    "test": "pnpm --filter \"./packages/*\" --filter \"./apps/*\" -r --if-present test",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage",
     "test:e2e": "pnpm --filter @ketopath/web test:e2e",
     "db:generate": "pnpm --filter @ketopath/db db:generate",
     "db:migrate": "pnpm --filter @ketopath/db db:migrate",
@@ -40,7 +42,9 @@
     "lint-staged": "^15.2.2",
     "prettier": "^3.2.5",
     "prettier-plugin-tailwindcss": "^0.5.14",
-    "typescript": "5.4.5"
+    "typescript": "5.4.5",
+    "vitest": "^1.6.0",
+    "@vitest/coverage-v8": "^1.6.0"
   },
   "lint-staged": {
     "*.{ts,tsx,js,jsx,cjs,mjs}": [
diff --git a/packages/shared/package.json b/packages/shared/package.json
index 5fb63ef..0db2b1a 100644
--- a/packages/shared/package.json
+++ b/packages/shared/package.json
@@ -10,7 +10,9 @@
   },
   "scripts": {
     "typecheck": "tsc --noEmit",
-    "lint": "eslint src --max-warnings=0"
+    "lint": "eslint src --max-warnings=0",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "devDependencies": {
     "@ketopath/eslint-config": "workspace:*",
diff --git a/packages/shared/src/index.ts b/packages/shared/src/index.ts
index cb0ff5c..6fac531 100644
--- a/packages/shared/src/index.ts
+++ b/packages/shared/src/index.ts
@@ -1 +1,3 @@
-export {};
+export * from './nutrition/bmr.js';
+export * from './nutrition/tdee.js';
+export * from './nutrition/types.js';
diff --git a/packages/shared/src/nutrition/bmr.test.ts b/packages/shared/src/nutrition/bmr.test.ts
new file mode 100644
index 0000000..3a52c42
--- /dev/null
+++ b/packages/shared/src/nutrition/bmr.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+
+import { calculateBmr } from './bmr.js';
+
+describe('calculateBmr (Mifflin-St Jeor)', () => {
+  it('matches the male formula for the "Michele" PRD persona', () => {
+    // 49 anni, uomo, 76 kg, 170 cm
+    // 10·76 + 6.25·170 − 5·49 + 5 = 760 + 1062.5 − 245 + 5 = 1582.5
+    const bmr = calculateBmr({ weightKg: 76, heightCm: 170, ageYears: 49, gender: 'MALE' });
+    expect(bmr).toBeCloseTo(1582.5, 2);
+  });
+
+  it('matches the female formula for the "Laura" PRD persona', () => {
+    // 46 anni, donna, 70 kg, 165 cm
+    // 10·70 + 6.25·165 − 5·46 − 161 = 700 + 1031.25 − 230 − 161 = 1340.25
+    const bmr = calculateBmr({ weightKg: 70, heightCm: 165, ageYears: 46, gender: 'FEMALE' });
+    expect(bmr).toBeCloseTo(1340.25, 2);
+  });
+
+  it('uses the average sex-constant for OTHER', () => {
+    const male = calculateBmr({ weightKg: 70, heightCm: 170, ageYears: 30, gender: 'MALE' });
+    const female = calculateBmr({ weightKg: 70, heightCm: 170, ageYears: 30, gender: 'FEMALE' });
+    const other = calculateBmr({ weightKg: 70, heightCm: 170, ageYears: 30, gender: 'OTHER' });
+    expect(other).toBeCloseTo((male + female) / 2, 5);
+  });
+
+  it.each([
+    { weightKg: 0, heightCm: 170, ageYears: 30 },
+    { weightKg: 70, heightCm: 0, ageYears: 30 },
+    { weightKg: 70, heightCm: 170, ageYears: 0 },
+    { weightKg: -1, heightCm: 170, ageYears: 30 },
+  ])('rejects non-positive inputs %j', (input) => {
+    expect(() => calculateBmr({ ...input, gender: 'MALE' })).toThrow(RangeError);
+  });
+});
diff --git a/packages/shared/src/nutrition/bmr.ts b/packages/shared/src/nutrition/bmr.ts
new file mode 100644
index 0000000..f8dc921
--- /dev/null
+++ b/packages/shared/src/nutrition/bmr.ts
@@ -0,0 +1,27 @@
+import type { Gender } from './types.js';
+
+export interface BmrInput {
+  weightKg: number;
+  heightCm: number;
+  ageYears: number;
+  gender: Gender;
+}
+
+// Mifflin-St Jeor equation. For Gender 'OTHER' we use the average of the
+// male and female sex-specific constants (-78), as a neutral approximation.
+export function calculateBmr({ weightKg, heightCm, ageYears, gender }: BmrInput): number {
+  if (weightKg <= 0 || heightCm <= 0 || ageYears <= 0) {
+    throw new RangeError('weightKg, heightCm and ageYears must be positive');
+  }
+
+  const base = 10 * weightKg + 6.25 * heightCm - 5 * ageYears;
+
+  switch (gender) {
+    case 'MALE':
+      return base + 5;
+    case 'FEMALE':
+      return base - 161;
+    case 'OTHER':
+      return base - 78;
+  }
+}
diff --git a/packages/shared/src/nutrition/tdee.test.ts b/packages/shared/src/nutrition/tdee.test.ts
new file mode 100644
index 0000000..caf82a4
--- /dev/null
+++ b/packages/shared/src/nutrition/tdee.test.ts
@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest';
+
+import { calculateBmr } from './bmr.js';
+import { calculateTdee } from './tdee.js';
+
+describe('calculateTdee', () => {
+  it('multiplies BMR by sedentary factor 1.2 for "Michele"', () => {
+    const bmr = calculateBmr({ weightKg: 76, heightCm: 170, ageYears: 49, gender: 'MALE' });
+    expect(calculateTdee(bmr, 'SEDENTARY')).toBeCloseTo(1899, 1);
+  });
+
+  it('multiplies BMR by moderate factor 1.55 for "Laura"', () => {
+    const bmr = calculateBmr({ weightKg: 70, heightCm: 165, ageYears: 46, gender: 'FEMALE' });
+    expect(calculateTdee(bmr, 'MODERATE')).toBeCloseTo(2077.39, 2);
+  });
+
+  it.each([
+    ['SEDENTARY', 1.2],
+    ['LIGHT', 1.375],
+    ['MODERATE', 1.55],
+    ['INTENSE', 1.725],
+  ] as const)('applies the %s multiplier (%f)', (level, factor) => {
+    expect(calculateTdee(2000, level)).toBeCloseTo(2000 * factor, 5);
+  });
+
+  it('rejects non-positive BMR', () => {
+    expect(() => calculateTdee(0, 'SEDENTARY')).toThrow(RangeError);
+    expect(() => calculateTdee(-1, 'SEDENTARY')).toThrow(RangeError);
+  });
+});
diff --git a/packages/shared/src/nutrition/tdee.ts b/packages/shared/src/nutrition/tdee.ts
new file mode 100644
index 0000000..30433f7
--- /dev/null
+++ b/packages/shared/src/nutrition/tdee.ts
@@ -0,0 +1,8 @@
+import { ACTIVITY_MULTIPLIERS, type ActivityLevel } from './types.js';
+
+export function calculateTdee(bmr: number, activityLevel: ActivityLevel): number {
+  if (bmr <= 0) {
+    throw new RangeError('bmr must be positive');
+  }
+  return bmr * ACTIVITY_MULTIPLIERS[activityLevel];
+}
diff --git a/packages/shared/src/nutrition/types.ts b/packages/shared/src/nutrition/types.ts
new file mode 100644
index 0000000..888d624
--- /dev/null
+++ b/packages/shared/src/nutrition/types.ts
@@ -0,0 +1,10 @@
+export type Gender = 'MALE' | 'FEMALE' | 'OTHER';
+
+export type ActivityLevel = 'SEDENTARY' | 'LIGHT' | 'MODERATE' | 'INTENSE';
+
+export const ACTIVITY_MULTIPLIERS: Record<ActivityLevel, number> = {
+  SEDENTARY: 1.2,
+  LIGHT: 1.375,
+  MODERATE: 1.55,
+  INTENSE: 1.725,
+};
diff --git a/packages/shared/vitest.config.ts b/packages/shared/vitest.config.ts
new file mode 100644
index 0000000..f46f517
--- /dev/null
+++ b/packages/shared/vitest.config.ts
@@ -0,0 +1,21 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    name: '@ketopath/shared',
+    environment: 'node',
+    include: ['src/**/*.test.ts'],
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'html'],
+      include: ['src/**/*.ts'],
+      exclude: ['src/**/*.test.ts', 'src/index.ts'],
+      thresholds: {
+        statements: 70,
+        branches: 70,
+        functions: 70,
+        lines: 70,
+      },
+    },
+  },
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index acb7b3d..6046057 100644
Binary files a/pnpm-lock.yaml and b/pnpm-lock.yaml differ
diff --git a/vitest.workspace.ts b/vitest.workspace.ts
new file mode 100644
index 0000000..9a6c8cb
--- /dev/null
+++ b/vitest.workspace.ts
@@ -0,0 +1,3 @@
+import { defineWorkspace } from 'vitest/config';
+
+export default defineWorkspace(['./packages/shared']);