:root {
  --bg: #f7f3e8;
  --panel: #fffaf0;
  --line: #263238;
  --soft: #d8cfc0;
  --text: #17212b;
  --muted: #68727b;
  --accent: #2a9d8f;
  --given: #e9dcc7;
  --selected: #ffe8a3;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color-scheme: light;
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); }
button { border: 0; color: inherit; font: inherit; cursor: pointer; -webkit-tap-highlight-color: transparent; }
.app-shell { width: min(620px, 100%); min-height: 100dvh; margin: 0 auto; padding: 16px 14px 22px; }
.topbar, .status-panel { display: flex; gap: 12px; align-items: center; justify-content: space-between; }
.eyebrow, .status-label { margin: 0 0 4px; color: var(--accent); font-size: .76rem; font-weight: 900; text-transform: uppercase; }
h1 { margin: 0; font-size: clamp(2rem, 9vw, 3.2rem); line-height: .95; }
.icon-button, .secondary, .keypad button { min-height: 42px; border-radius: 8px; background: var(--panel); border: 1px solid var(--soft); font-weight: 900; }
.icon-button { width: 46px; }
.secondary { padding: 0 14px; }
.sudoku-actions { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.status-panel { margin-top: 12px; padding: 14px; border: 1px solid var(--soft); border-radius: 8px; background: var(--panel); }
.status-text, .note { margin: 0; color: var(--muted); line-height: 1.35; }
.board { display: grid; grid-template-columns: repeat(9, minmax(0, 1fr)); margin-top: 14px; border: 2px solid var(--line); background: var(--line); gap: 1px; }
.cell { display: grid; place-items: center; aspect-ratio: 1; background: var(--panel); font-size: clamp(1.1rem, 7vw, 2rem); font-weight: 900; }
.cell.given { background: var(--given); }
.cell.selected { background: var(--selected); }
.cell:nth-child(3n) { border-right: 2px solid var(--line); }
.cell:nth-child(9n) { border-right: 0; }
.cell:nth-child(n+19):nth-child(-n+27), .cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--line); }
.keypad { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 8px; margin-top: 12px; }
.keypad button { background: #ffffff; }
.keypad button.clear { color: #b91c1c; }
.note { margin-top: 10px; text-align: center; }