:root{--bg: #ffffff;--text: #111111;--muted: #6b7280;--card: #f3f4f6;--border: #e5e7eb;--accent: #2563eb;--button-bg: #2563eb;--button-text: #ffffff;--nav-active-bg: #e5e7eb}:root[data-theme=dark]{--bg: #0b0f14;--text: #f3f4f6;--muted: #9aa3af;--card: #1f2937;--border: #374151;--accent: #60a5fa;--button-bg: #374151;--button-text: #f3f4f6;--nav-active-bg: #374151}body{margin:0;font-family:system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif;background:var(--bg);color:var(--text)}.container{max-width:900px;margin:0 auto;padding:16px}.header{display:flex;align-items:center;justify-content:space-between;padding:12px 0;border-bottom:1px solid var(--border)}.nav{display:flex;gap:12px}.nav-link{text-decoration:none;color:var(--text);padding:6px 10px;border-radius:6px;transition:background .2s,color .2s}.nav-link.active{background:var(--nav-active-bg);font-weight:600}button{background:var(--button-bg);color:var(--button-text);border:1px solid var(--border);padding:6px 12px;border-radius:6px;cursor:pointer;transition:background .2s,color .2s}button:hover{opacity:.85}.page{padding:20px 0}.todo-form{display:flex;gap:8px;margin-bottom:12px}.todo-form input{flex:1;padding:8px 10px;border-radius:6px;border:1px solid var(--border);background:transparent;color:var(--text)}.todo-form button{background:var(--accent);color:#fff;border:none;border-radius:6px;padding:8px 12px}.todo-list{list-style:none;padding:0;margin:0;display:grid;gap:6px}.todo-list li{display:flex;align-items:center;justify-content:space-between;padding:6px 10px;border:1px solid var(--border);border-radius:6px;background:var(--card)}.todo-list li.done span{text-decoration:line-through;color:var(--muted)}.todo-list li button{background:#ef4444;color:#fff;border:none;border-radius:4px;padding:2px 6px}