* { box-sizing: border-box; }
body { margin: 0; font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', sans-serif; background: #f3f5f9; color: #1f2937; }
.app { max-width: 480px; margin: 0 auto; min-height: 100vh; padding: 12px; }
.topbar { margin-bottom: 10px; }
.title { font-size: 24px; font-weight: 700; }
.meta { color: #6b7280; font-size: 13px; }
.panel, .actions, .status { display: flex; gap: 8px; margin: 10px 0; flex-wrap: wrap; }
.btn { flex: 1; border: 0; border-radius: 10px; padding: 10px 12px; font-size: 15px; background: #2563eb; color: #fff; }
.btn.secondary { background: #4b5563; }
.btn.success { background: #059669; }
.btn:disabled { opacity: 0.55; }
.status span { background: #fff; border-radius: 8px; padding: 6px 10px; font-size: 13px; }
.board-wrap { background: #fff; border-radius: 12px; padding: 8px; box-shadow: 0 8px 20px rgba(0,0,0,.08); }
.board { display: grid; grid-template-columns: repeat(9, 1fr); border: 2px solid #111827; }
.cell { width: 100%; aspect-ratio: 1/1; border: 1px solid #d1d5db; display: flex; align-items: center; justify-content: center; font-size: 19px; font-weight: 600; background: #fff; }
.cell.fixed { background: #e5e7eb; color: #111827; }
.cell.active { background: #dbeafe; }
.cell.same { background: #eff6ff; }
.cell.error { color: #dc2626; }
.cell .note { font-size: 10px; line-height: 1.1; color: #4b5563; text-align: center; padding: 2px; white-space: pre-wrap; }
.cell.b3r { border-bottom: 2px solid #111827; }
.cell.b3c { border-right: 2px solid #111827; }
.keypad { margin-top: 12px; display: grid; grid-template-columns: repeat(9, 1fr); gap: 6px; }
.key { border: 0; border-radius: 8px; background: #fff; padding: 10px 0; font-size: 16px; box-shadow: 0 2px 6px rgba(0,0,0,.06); }
@media (max-width: 360px){ .cell { font-size: 16px; } }