feat: complete Phase 1 - project foundation with Next.js 16 and Tailwind CSS 4

Initialize modern tech stack following audio-ui patterns:

**Framework Setup**
- Next.js 16 with App Router and Turbopack (ready in 754ms)
- React 19 with TypeScript 5
- Static export configuration for deployment

**Styling System**
- Tailwind CSS 4 with @tailwindcss/postcss
- OKLCH color space for vibrant, perceptually uniform colors
- Custom CSS variables for theming (light/dark modes)
- Canvas-specific color palette (canvas-bg, canvas-grid, canvas-selection)
- Custom animations (fadeIn, slideDown, scaleIn, etc.)
- Checkerboard pattern utility for transparency preview
- Custom scrollbar styling

**State Management**
- Zustand installed for layers, canvas, and history state

**Canvas Libraries**
- pica for high-quality image resizing
- file-saver for export functionality
- uuid for layer ID generation

**Development Experience**
- Path aliases (@/* pattern) configured
- Strict TypeScript with proper type checking
- Auto dark mode detection with localStorage persistence
- Responsive layout with overflow handling

**Initial UI**
- Root layout with theme system
- Landing page showing Phase 1 completion status
- Clean, modern design with gradient title

Ready for Phase 2: Core Canvas Engine implementation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/globals.css

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+@import "tailwindcss";
+
+/* Source directives - scan components for Tailwind classes */
+@source "../components/editor/*.{js,ts,jsx,tsx}";
+@source "../components/canvas/*.{js,ts,jsx,tsx}";
+@source "../components/tools/*.{js,ts,jsx,tsx}";
+@source "../components/layers/*.{js,ts,jsx,tsx}";
+@source "../components/effects/*.{js,ts,jsx,tsx}";
+@source "../components/colors/*.{js,ts,jsx,tsx}";
+@source "../components/modals/*.{js,ts,jsx,tsx}";
+@source "../components/ui/*.{js,ts,jsx,tsx}";
+@source "*.{js,ts,jsx,tsx}";
+
+/* Custom dark mode variant */
+@custom-variant dark (&:is(.dark *));
+
+/* CSS Variables for theming */
+@layer base {
+  :root {
+    /* Light mode colors using OKLCH - creative palette for design tools */
+    --background: oklch(98% 0.02 220);
+    --foreground: oklch(18% 0.08 270);
+
+    --card: oklch(99% 0.01 220);
+    --card-foreground: oklch(18% 0.08 270);
+
+    --popover: oklch(99% 0.01 220);
+    --popover-foreground: oklch(18% 0.08 270);
+
+    --primary: oklch(56% 0.25 265);
+    --primary-foreground: oklch(99% 0.01 220);
+
+    --secondary: oklch(92% 0.06 240);
+    --secondary-foreground: oklch(22% 0.12 270);
+
+    --muted: oklch(94% 0.04 230);
+    --muted-foreground: oklch(42% 0.10 260);
+
+    --accent: oklch(88% 0.10 200);
+    --accent-foreground: oklch(22% 0.15 270);
+
+    --destructive: oklch(58% 0.26 25);
+    --destructive-foreground: oklch(99% 0.01 220);
+
+    --border: oklch(86% 0.06 230);
+    --input: oklch(92% 0.05 230);
+    --ring: oklch(56% 0.25 265);
+
+    --radius: 0.5rem;
+
+    --success: oklch(58% 0.22 150);
+    --success-foreground: oklch(99% 0.01 220);
+
+    --warning: oklch(68% 0.22 80);
+    --warning-foreground: oklch(18% 0.08 270);
+
+    --info: oklch(60% 0.22 240);
+    --info-foreground: oklch(99% 0.01 220);
+
+    /* Canvas-specific colors */
+    --canvas-bg: oklch(96% 0.01 220);
+    --canvas-grid: oklch(88% 0.03 230);
+    --canvas-selection: oklch(56% 0.25 265 / 0.3);
+    --canvas-selection-border: oklch(56% 0.25 265);
+    --ruler-bg: oklch(94% 0.03 220);
+    --ruler-fg: oklch(40% 0.08 260);
+  }
+
+  .dark {
+    /* Dark mode colors using OKLCH - professional design tool palette */
+    --background: oklch(16% 0.015 270);
+    --foreground: oklch(92% 0.02 220);
+
+    --card: oklch(19% 0.02 275);
+    --card-foreground: oklch(92% 0.02 220);
+
+    --popover: oklch(19% 0.02 275);
+    --popover-foreground: oklch(92% 0.02 220);
+
+    --primary: oklch(72% 0.22 270);
+    --primary-foreground: oklch(19% 0.02 275);
+
+    --secondary: oklch(23% 0.03 280);
+    --secondary-foreground: oklch(85% 0.12 220);
+
+    --muted: oklch(21% 0.02 275);
+    --muted-foreground: oklch(64% 0.08 240);
+
+    --accent: oklch(26% 0.03 285);
+    --accent-foreground: oklch(82% 0.18 260);
+
+    --destructive: oklch(62% 0.24 25);
+    --destructive-foreground: oklch(92% 0.02 220);
+
+    --border: oklch(32% 0.04 280);
+    --input: oklch(23% 0.03 280);
+    --ring: oklch(72% 0.22 270);
+
+    --success: oklch(68% 0.20 150);
+    --success-foreground: oklch(19% 0.02 275);
+
+    --warning: oklch(72% 0.20 80);
+    --warning-foreground: oklch(19% 0.02 275);
+
+    --info: oklch(68% 0.20 240);
+    --info-foreground: oklch(19% 0.02 275);
+
+    /* Canvas-specific colors */
+    --canvas-bg: oklch(14% 0.015 270);
+    --canvas-grid: oklch(28% 0.03 280);
+    --canvas-selection: oklch(72% 0.22 270 / 0.25);
+    --canvas-selection-border: oklch(72% 0.22 270);
+    --ruler-bg: oklch(18% 0.02 275);
+    --ruler-fg: oklch(68% 0.08 240);
+  }
+}
+
+/* Theme inline - map CSS variables to Tailwind colors */
+@theme inline {
+  --color-background: var(--background);
+  --color-foreground: var(--foreground);
+  --color-card: var(--card);
+  --color-card-foreground: var(--card-foreground);
+  --color-popover: var(--popover);
+  --color-popover-foreground: var(--popover-foreground);
+  --color-primary: var(--primary);
+  --color-primary-foreground: var(--primary-foreground);
+  --color-secondary: var(--secondary);
+  --color-secondary-foreground: var(--secondary-foreground);
+  --color-muted: var(--muted);
+  --color-muted-foreground: var(--muted-foreground);
+  --color-accent: var(--accent);
+  --color-accent-foreground: var(--accent-foreground);
+  --color-destructive: var(--destructive);
+  --color-destructive-foreground: var(--destructive-foreground);
+  --color-border: var(--border);
+  --color-input: var(--input);
+  --color-ring: var(--ring);
+  --color-success: var(--success);
+  --color-success-foreground: var(--success-foreground);
+  --color-warning: var(--warning);
+  --color-warning-foreground: var(--warning-foreground);
+  --color-info: var(--info);
+  --color-info-foreground: var(--info-foreground);
+  --color-canvas-bg: var(--canvas-bg);
+  --color-canvas-grid: var(--canvas-grid);
+  --color-canvas-selection: var(--canvas-selection);
+  --color-canvas-selection-border: var(--canvas-selection-border);
+  --color-ruler-bg: var(--ruler-bg);
+  --color-ruler-fg: var(--ruler-fg);
+
+  --radius: var(--radius);
+}
+
+/* Global styles */
+@layer base {
+  * {
+    @apply border-border;
+  }
+
+  body {
+    @apply bg-background text-foreground;
+    font-feature-settings: "rlig" 1, "calt" 1;
+  }
+
+  /* Apply custom scrollbar globally */
+  * {
+    scrollbar-width: thin;
+  }
+
+  *::-webkit-scrollbar {
+    width: 10px;
+    height: 10px;
+  }
+
+  *::-webkit-scrollbar-track {
+    background: var(--muted);
+    border-radius: 5px;
+  }
+
+  *::-webkit-scrollbar-thumb {
+    background: color-mix(in oklch, var(--muted-foreground) 30%, transparent);
+    border-radius: 5px;
+    border: 2px solid var(--muted);
+    transition: background 0.2s ease;
+  }
+
+  *::-webkit-scrollbar-thumb:hover {
+    background: color-mix(in oklch, var(--muted-foreground) 50%, transparent);
+  }
+
+  *::-webkit-scrollbar-thumb:active {
+    background: color-mix(in oklch, var(--muted-foreground) 70%, transparent);
+  }
+
+  /* Scrollbar corners */
+  *::-webkit-scrollbar-corner {
+    background: var(--muted);
+  }
+}
+
+/* Custom animations */
+@layer utilities {
+  @keyframes fadeIn {
+    from {
+      opacity: 0;
+    }
+    to {
+      opacity: 1;
+    }
+  }
+
+  @keyframes slideInFromRight {
+    from {
+      transform: translateX(100%);
+      opacity: 0;
+    }
+    to {
+      transform: translateX(0);
+      opacity: 1;
+    }
+  }
+
+  @keyframes slideDown {
+    from {
+      transform: translateY(-10px);
+      opacity: 0;
+    }
+    to {
+      transform: translateY(0);
+      opacity: 1;
+    }
+  }
+
+  @keyframes slideUp {
+    from {
+      transform: translateY(10px);
+      opacity: 0;
+    }
+    to {
+      transform: translateY(0);
+      opacity: 1;
+    }
+  }
+
+  @keyframes scaleIn {
+    from {
+      transform: scale(0.95);
+      opacity: 0;
+    }
+    to {
+      transform: scale(1);
+      opacity: 1;
+    }
+  }
+
+  @keyframes pulseSubtle {
+    0%, 100% {
+      opacity: 1;
+    }
+    50% {
+      opacity: 0.8;
+    }
+  }
+
+  @keyframes shimmer {
+    0% {
+      background-position: -1000px 0;
+    }
+    100% {
+      background-position: 1000px 0;
+    }
+  }
+
+  @keyframes spin {
+    from {
+      transform: rotate(0deg);
+    }
+    to {
+      transform: rotate(360deg);
+    }
+  }
+
+  .animate-fadeIn {
+    animation: fadeIn 0.2s ease-out;
+  }
+
+  .animate-slideInFromRight {
+    animation: slideInFromRight 0.3s ease-out;
+  }
+
+  .animate-slideDown {
+    animation: slideDown 0.3s ease-out;
+  }
+
+  .animate-slideUp {
+    animation: slideUp 0.3s ease-out;
+  }
+
+  .animate-scaleIn {
+    animation: scaleIn 0.2s ease-out;
+  }
+
+  .animate-pulseSubtle {
+    animation: pulseSubtle 2s ease-in-out infinite;
+  }
+
+  .animate-shimmer {
+    animation: shimmer 2s linear infinite;
+  }
+
+  .animate-spin {
+    animation: spin 1s linear infinite;
+  }
+}
+
+/* Canvas-specific utilities */
+@layer utilities {
+  .checkerboard {
+    background-image:
+      linear-gradient(45deg, oklch(86% 0.01 220) 25%, transparent 25%),
+      linear-gradient(-45deg, oklch(86% 0.01 220) 25%, transparent 25%),
+      linear-gradient(45deg, transparent 75%, oklch(86% 0.01 220) 75%),
+      linear-gradient(-45deg, transparent 75%, oklch(86% 0.01 220) 75%);
+    background-size: 20px 20px;
+    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
+  }
+
+  .dark .checkerboard {
+    background-image:
+      linear-gradient(45deg, oklch(22% 0.02 270) 25%, transparent 25%),
+      linear-gradient(-45deg, oklch(22% 0.02 270) 25%, transparent 25%),
+      linear-gradient(45deg, transparent 75%, oklch(22% 0.02 270) 75%),
+      linear-gradient(-45deg, transparent 75%, oklch(22% 0.02 270) 75%);
+    background-size: 20px 20px;
+    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
+  }
+}

app/layout.tsx

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+import type { Metadata } from 'next';
+import './globals.css';
+
+export const metadata: Metadata = {
+  title: 'Paint UI - Browser Image Editor',
+  description: 'Modern browser-based image editor built with Next.js. Multi-layer canvas, drawing tools, effects, and more.',
+  keywords: ['image editor', 'canvas', 'drawing', 'paint', 'layers', 'effects', 'photoshop alternative'],
+};
+
+export default function RootLayout({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  return (
+    <html lang="en" suppressHydrationWarning>
+      <head>
+        <script
+          dangerouslySetInnerHTML={{
+            __html: `
+              (function() {
+                try {
+                  const theme = localStorage.getItem('theme');
+                  const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
+                  const shouldBeDark = theme === 'dark' || (!theme && prefersDark);
+                  if (shouldBeDark) {
+                    document.documentElement.classList.add('dark');
+                  }
+                } catch (e) {}
+              })();
+            `,
+          }}
+        />
+      </head>
+      <body className="min-h-screen antialiased overflow-hidden">
+        {children}
+      </body>
+    </html>
+  );
+}

app/page.tsx

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+export default function HomePage() {
+  return (
+    <main className="flex min-h-screen flex-col items-center justify-center bg-background p-8">
+      <div className="max-w-2xl space-y-6 text-center">
+        <h1 className="text-6xl font-bold bg-gradient-to-r from-primary via-accent to-primary bg-clip-text text-transparent">
+          Paint UI
+        </h1>
+        <p className="text-xl text-muted-foreground">
+          Modern browser-based image editor
+        </p>
+        <div className="grid grid-cols-2 gap-4 pt-8 text-left">
+          <div className="space-y-2 rounded-lg border border-border bg-card p-4">
+            <h3 className="font-semibold text-card-foreground">Phase 1: Foundation</h3>
+            <ul className="space-y-1 text-sm text-muted-foreground">
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Next.js 16 setup
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Tailwind CSS 4
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> TypeScript config
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Theme system
+              </li>
+            </ul>
+          </div>
+          <div className="space-y-2 rounded-lg border border-border bg-card p-4">
+            <h3 className="font-semibold text-card-foreground">Coming Soon</h3>
+            <ul className="space-y-1 text-sm text-muted-foreground">
+              <li>Canvas rendering</li>
+              <li>Layer system</li>
+              <li>Drawing tools</li>
+              <li>Effects & filters</li>
+            </ul>
+          </div>
+        </div>
+        <p className="pt-4 text-sm text-muted-foreground">
+          Built with Next.js 16 • React 19 • Tailwind CSS 4
+        </p>
+      </div>
+    </main>
+  );
+}

next.config.ts

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+import type { NextConfig } from 'next';
+
+const nextConfig: NextConfig = {
+  output: 'export',
+  reactStrictMode: true,
+  // Turbopack configuration (Next.js 16+)
+  turbopack: {},
+  // Webpack fallback for older Next.js versions
+  webpack: (config) => {
+    // Required for Canvas API and Web Workers
+    config.resolve.fallback = {
+      ...config.resolve.fallback,
+      fs: false,
+      path: false,
+      crypto: false,
+    };
+
+    return config;
+  },
+};
+
+export default nextConfig;

package.json

@@ -0,0 +1,36 @@
+{
+  "name": "paint-ui",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev --turbopack",
+    "build": "next build",
+    "start": "next start",
+    "lint": "next lint"
+  },
+  "dependencies": {
+    "clsx": "^2.1.1",
+    "file-saver": "^2.0.5",
+    "lucide-react": "^0.553.0",
+    "next": "^16.0.0",
+    "pica": "^9.0.1",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "tailwind-merge": "^3.3.1",
+    "uuid": "^11.0.4",
+    "zustand": "^5.0.2"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4.1.17",
+    "@types/file-saver": "^2.0.7",
+    "@types/node": "^22",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "@types/uuid": "^10.0.0",
+    "eslint": "^9",
+    "eslint-config-next": "^16.0.0",
+    "tailwindcss": "^4.0.0",
+    "typescript": "^5"
+  },
+  "packageManager": "pnpm@9.0.0"
+}

postcss.config.js

@@ -0,0 +1,8 @@
+/** @type {import('postcss-load-config').Config} */
+const config = {
+  plugins: {
+    '@tailwindcss/postcss': {},
+  },
+};
+
+module.exports = config;

tsconfig.json

@@ -0,0 +1,41 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "lib": [
+      "dom",
+      "dom.iterable",
+      "esnext"
+    ],
+    "allowJs": true,
+    "skipLibCheck": true,
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "jsx": "react-jsx",
+    "incremental": true,
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
+    "paths": {
+      "@/*": [
+        "./*"
+      ]
+    }
+  },
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts"
+  ],
+  "exclude": [
+    "node_modules"
+  ]
+}