:root {
  --color-bg: #050505;
  --color-surface: #111;
  --color-border: #2a2a2a;
  --color-text: #f5f5f5;
  --color-muted: #9ca3af;
  --color-accent: #4dd0e1;
  --color-success: #6ee7b7;
  --color-danger: #f87171;
  --font-base: "Segoe UI", Roboto, "Noto Sans JP", sans-serif;
  --transition-fast: 120ms ease-out;
  --cell-min-size: 48px;
  --app-max-width: 960px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-base);
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
}

body:focus-visible {
  outline: none;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  border: 0;
  clip: rect(0 0 0 0);
  overflow: hidden;
}

.app {
  margin: 0 auto;
  min-height: 100vh;
  max-width: var(--app-max-width);
  display: flex;
  flex-direction: column;
  padding: 0 1rem 1.5rem;
  gap: 1rem;
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 0.5rem 0.5rem;
  gap: 1rem;
}

.app-logo {
  font-size: 1.25rem;
  font-weight: 700;
}

.app-nav {
  display: flex;
  gap: 0.5rem;
}

.nav-button,
.icon-button,
.control-button {
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: 0.5rem;
  padding: 0.5rem 0.9rem;
  font-size: 0.95rem;
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast);
  min-width: 3rem;
}

.nav-button:hover,
.icon-button:hover,
.control-button:hover,
.nav-button:focus-visible,
.icon-button:focus-visible,
.control-button:focus-visible {
  background: var(--color-accent);
  color: #031215;
  outline: none;
}

.nav-button[aria-current="true"] {
  background: var(--color-accent);
  color: #031215;
}

.icon-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.app-main {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

.board-wrapper {
  width: min(90vw, 540px);
  position: relative;
}

.board {
  width: 100%;
  aspect-ratio: 1 / 1;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 1rem;
  padding: 0.75rem;
  display: grid;
  gap: 0.5rem;
  grid-template-columns: repeat(var(--grid-size, 6), 1fr);
  touch-action: manipulation;
  position: relative;
}

.nr-cell {
  min-height: var(--cell-min-size);
  border-radius: 0.75rem;
  border: 1px solid var(--color-border);
  background: #1b1b1d;
  color: var(--color-text);
  font-size: clamp(1rem, 2.4vw, 1.5rem);
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast), border-color var(--transition-fast);
}

.nr-cell:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.nr-cell--target {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(77, 208, 225, 0.4);
}

.nr-cell--cleared {
  background: #0e2a2f;
  color: var(--color-accent);
  transform: scale(0.94);
}

.nr-cell--dummy {
  color: var(--color-text);
}

.nr-cell--mistake {
  background: var(--color-danger);
  color: #000;
}

.board--flash {
  animation: board-flash 0.2s ease-in;
}

@keyframes board-flash {
  from {
    box-shadow: 0 0 0 0 rgba(248, 113, 113, 0.7);
  }
  to {
    box-shadow: 0 0 0 24px rgba(248, 113, 113, 0);
  }
}

.countdown {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(3rem, 12vw, 5rem);
  font-weight: 700;
  background: rgba(5, 5, 5, 0.75);
  border-radius: 1rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast);
}

.countdown[aria-hidden="false"] {
  opacity: 1;
}

.app-footer {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 1rem;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.footer-primary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 0.75rem;
}

.metric {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.metric-label {
  font-size: 0.85rem;
  color: var(--color-muted);
}

.metric-value {
  font-size: 1.25rem;
  font-weight: 600;
}

.control-group {
  display: flex;
  gap: 0.5rem;
}

.control-button[disabled] {
  opacity: 0.45;
  cursor: not-allowed;
}

.footer-secondary {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  font-size: 0.9rem;
  color: var(--color-muted);
}

.progress {
  width: 100%;
  height: 0.5rem;
  background: #1f1f21;
  border-radius: 999px;
  overflow: hidden;
}

.progress-fill {
  width: 0;
  height: 100%;
  background: var(--color-accent);
  transition: width 200ms ease-out;
}

.toast-container {
  position: fixed;
  inset-inline: 0;
  bottom: 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  pointer-events: none;
  padding: 0 1rem;
  z-index: 40;
}

.toast {
  background: rgba(17, 17, 17, 0.9);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  padding: 0.75rem 1.25rem;
  border-radius: 999px;
  transform: translateY(20px);
  opacity: 0;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
  pointer-events: auto;
}

.toast--visible {
  transform: translateY(0);
  opacity: 1;
}

.toast--error {
  border-color: var(--color-danger);
  color: var(--color-danger);
}

.dialog-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  z-index: 50;
}

.dialog {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 1rem;
  max-width: min(420px, 90vw);
  width: 100%;
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.dialog-title {
  margin: 0;
  font-size: 1.5rem;
}

.dialog-body {
  font-size: 0.95rem;
  color: var(--color-text);
}

.dialog-footer {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
}

.dialog-button {
  border-radius: 0.5rem;
  border: 1px solid var(--color-border);
  background: var(--color-accent);
  color: #031215;
  font-weight: 600;
  padding: 0.5rem 0.9rem;
}

.dialog-button--secondary {
  background: transparent;
  color: var(--color-text);
}

@media (max-width: 480px) {
  :root {
    --cell-min-size: 42px;
  }
  .app {
    padding: 0 0.75rem 1rem;
  }
  .app-header {
    flex-direction: column;
    align-items: stretch;
  }
  .app-nav {
    justify-content: center;
  }
  .footer-primary {
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  }
}
.settings-panel {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.settings-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.settings-group {
  border: 1px solid var(--color-border);
  border-radius: 0.75rem;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.settings-group legend {
  padding: 0 0.5rem;
  font-size: 0.95rem;
  color: var(--color-muted);
}

.settings-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.95rem;
}

.settings-row input[type="radio"],
.settings-row input[type="checkbox"] {
  margin-right: 0.5rem;
}

.settings-row span {
  flex: 1;
}

.settings-row select {
  width: 160px;
  border-radius: 0.5rem;
  border: 1px solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text);
  padding: 0.4rem 0.6rem;
}

.result-panel {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.result-grid {
  display: grid;
  gap: 0.5rem;
}

.result-row {
  display: flex;
  justify-content: space-between;
  font-size: 1rem;
  padding: 0.25rem 0;
}

.result-row span {
  color: var(--color-muted);
}

.result-badge {
  text-align: center;
  padding: 0.5rem 0;
  font-weight: 600;
  color: var(--color-accent);
}

.mode-description {
  margin: 0 0 0.75rem;
  font-size: 0.95rem;
  color: var(--color-muted);
}

.settings-row--stack {
  align-items: flex-start;
  flex-direction: column;
  justify-content: flex-start;
  gap: 0.4rem;
  width: 100%;
}

.settings-option {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.settings-hint {
  display: block;
  color: var(--color-muted);
  font-size: 0.82rem;
  line-height: 1.4;
}