:root {
  color-scheme: light;
  --paper: #f4efe4;
  --paper-2: #fffdf8;
  --ink: #22201c;
  --muted: #726c62;
  --line: #b9b1a4;
  --line-strong: #34302a;
  --fixed: #ddd4c4;
  --selected: #ebe3d5;
  --button: #2f2b26;
  --button-text: #fffdf8;
  --danger-soft: #efe5d8;
  --radius: 18px;
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: light only;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at top, rgba(255,255,255,.7), transparent 34rem),
    var(--paper);
  color: var(--ink);
  font-family: Georgia, "Times New Roman", serif;
}

button,
input {
  font: inherit;
}

button {
  -webkit-tap-highlight-color: transparent;
}

.app-shell {
  width: min(94vw, 760px);
  margin: 0 auto;
  padding: max(20px, env(safe-area-inset-top)) 0 max(28px, env(safe-area-inset-bottom));
}

.topbar {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 18px;
}

h1 {
  margin: 0;
  font-size: clamp(2rem, 7vw, 3.2rem);
  line-height: .95;
  letter-spacing: -.04em;
}

.subtitle {
  margin: 10px 0 0;
  color: var(--muted);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: clamp(.9rem, 2.4vw, 1rem);
  line-height: 1.45;
}

.difficulty {
  flex: 0 0 auto;
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: rgba(255,255,255,.35);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .02em;
}

.game-card {
  padding: clamp(14px, 3.5vw, 26px);
  border: 1px solid rgba(70, 62, 52, .18);
  border-radius: var(--radius);
  background: rgba(255,253,248,.76);
  box-shadow: 0 16px 50px rgba(68, 57, 43, .08);
  backdrop-filter: blur(4px);
}

.board {
  --cell: min(11.2vw, 74px);
  --gap: min(5.2vw, 35px);
  display: grid;
  grid-template-columns:
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell);
  grid-template-rows:
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell) var(--gap)
    var(--cell);
  width: max-content;
  max-width: 100%;
  margin: 4px auto 24px;
  align-items: center;
  justify-items: center;
}

.cell {
  width: var(--cell);
  height: var(--cell);
  border: 2px solid var(--line-strong);
  border-radius: 5px;
  background: rgba(255,255,255,.55);
  color: var(--ink);
  display: grid;
  place-items: center;
  font-size: clamp(1.35rem, 6vw, 2.35rem);
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
  user-select: none;
  touch-action: manipulation;
  outline: none;
}

.cell.fixed {
  background: var(--fixed);
  cursor: default;
}

.cell.selected:not(.fixed) {
  background: var(--selected);
  box-shadow: inset 0 0 0 2px rgba(34,32,28,.14);
}

.cell:focus-visible {
  box-shadow: 0 0 0 4px rgba(34,32,28,.16);
}

.constraint {
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
  color: var(--line-strong);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: clamp(1.15rem, 4vw, 1.9rem);
  font-weight: 800;
  line-height: 1;
  user-select: none;
}

.constraint.vertical {
  transform: rotate(90deg);
}

.number-pad {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 8px;
  max-width: 520px;
  margin: 0 auto;
}

.number-pad button {
  min-height: 48px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--paper-2);
  color: var(--ink);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 1.1rem;
  font-weight: 750;
  cursor: pointer;
  touch-action: manipulation;
}

.number-pad button.erase {
  background: #efe5d8;
  color: #6a3327;
  border-color: #c9a797;
}

.number-pad button:active {
  transform: translateY(1px);
}

.message {
  min-height: 26px;
  margin: 14px 0 2px;
  text-align: center;
  color: var(--muted);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .92rem;
  font-weight: 600;
}

.message.solved {
  color: var(--ink);
  font-weight: 800;
}

.actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 12px;
}

.action-button {
  min-height: 52px;
  border-radius: 12px;
  padding: 10px 14px;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-weight: 800;
  cursor: pointer;
  touch-action: manipulation;
  transition: transform .08s ease, background .15s ease, color .15s ease;
}

.action-button:active {
  transform: translateY(1px);
}

.action-button.primary {
  border: 1px solid var(--button);
  background: var(--button);
  color: var(--button-text);
}

.action-button.secondary {
  border: 1px solid var(--line-strong);
  background: transparent;
  color: var(--ink);
}

.action-button.confirming {
  background: var(--danger-soft);
  color: var(--ink);
  border-color: var(--line-strong);
}

footer {
  padding: 14px 8px 0;
  text-align: center;
  color: var(--muted);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .78rem;
}

footer p {
  margin: 0;
}

@media (max-width: 560px) {
  .app-shell {
    width: min(96vw, 520px);
  }

  .topbar {
    align-items: flex-start;
  }

  .difficulty {
    margin-top: 2px;
  }

  .game-card {
    padding: 12px 10px 16px;
    border-radius: 14px;
  }

  .board {
    --cell: 11.8vw;
    --gap: 3.7vw;
    margin-bottom: 18px;
  }

  .actions {
    gap: 8px;
  }

  .action-button {
    min-height: 50px;
    font-size: .9rem;
  }
}

@media (max-width: 390px) {
  .subtitle {
    max-width: 240px;
  }

  .difficulty {
    font-size: .68rem;
    padding: 6px 8px;
  }

  .board {
    --cell: 12vw;
    --gap: 3.1vw;
  }

  .cell {
    border-width: 1.7px;
  }

  .number-pad {
    gap: 6px;
  }

  .number-pad button {
    min-height: 44px;
    border-radius: 8px;
  }
}