/* ═══════════════════════════════════════════════════
   layout.css — screen system, loading, error, home,
                how-to-play, level select, leaderboard
════════════════════════════════════════════════════ */

/* ── Screen system ──────────────────────────────── */
.screen {
  position: fixed;
  inset: 0;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  overflow-x: hidden;
  background-color: var(--c-bg);

  /* Safe area padding */
  padding-top:    var(--safe-top);
  padding-bottom: var(--safe-bottom);
  padding-inline-start: var(--safe-left);
  padding-inline-end:   var(--safe-right);

  /* Hidden by default */
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition:
    opacity   var(--dur-normal) var(--ease-out),
    transform var(--dur-normal) var(--ease-out);
}

.screen--active {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
  z-index: 10;
}

/* ── Loading screen ─────────────────────────────── */
#screen-loading {
  align-items: center;
  justify-content: center;
  background-color: var(--c-bg);
  z-index: 100;
}

.loading-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-6);
}

.loading-logo {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--sp-1);
  font-size: var(--fs-3xl);
}

.logo-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  color: var(--c-accent);
  animation: logo-spin 2s ease-in-out infinite;
}
.logo-arrow:nth-child(1) { animation-delay: 0s; }
.logo-arrow:nth-child(2) { animation-delay: 0.15s; }
.logo-arrow:nth-child(3) { animation-delay: 0.3s; }
.logo-arrow:nth-child(4) { animation-delay: 0.45s; }

@keyframes logo-spin {
  0%, 80%, 100% { transform: scale(1); opacity: 1; }
  40%            { transform: scale(1.3) rotate(90deg); opacity: 0.6; }
}

.loading-text {
  color: var(--c-text-muted);
  font-size: var(--fs-sm);
  letter-spacing: 0.04em;
}

/* ── Error screen ───────────────────────────────── */
#screen-error {
  align-items: center;
  justify-content: center;
}

.error-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-4);
  padding: var(--sp-8);
  text-align: center;
  max-width: 360px;
}

.error-icon {
  font-size: 3rem;
  color: var(--c-danger);
}

.error-title {
  font-size: var(--fs-xl);
  color: var(--c-text);
}

.error-body {
  color: var(--c-text-muted);
  font-size: var(--fs-sm);
}

/* ── Home screen ────────────────────────────────── */
#screen-home {
  align-items: center;
  justify-content: space-between;
  padding-block: var(--sp-10);
  gap: var(--sp-6);
}

.home-header {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-2);
  text-align: center;
  padding-block-start: var(--sp-4);
}

.home-title {
  font-size: var(--fs-3xl);
  color: var(--c-accent);
  letter-spacing: -0.02em;
}

.home-subtitle {
  font-size: var(--fs-sm);
  color: var(--c-text-muted);
  max-width: 28ch;
  text-align: center;
}

.home-stats {
  display: flex;
  gap: var(--sp-4);
  justify-content: center;
  padding-inline: var(--sp-6);
}

.stat-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-1);
  background-color: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-lg);
  padding: var(--sp-4) var(--sp-6);
  flex: 1;
  max-width: 160px;
  box-shadow: var(--shadow-sm);
}

.stat-label {
  font-size: var(--fs-xs);
  color: var(--c-text-muted);
  font-weight: var(--fw-medium);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.stat-value {
  font-size: var(--fs-2xl);
  font-weight: var(--fw-bold);
  color: var(--c-score);
  font-variant-numeric: tabular-nums;
  line-height: 1;
}

.home-actions {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-3);
  width: 100%;
  padding-inline: var(--sp-8);
  max-width: 400px;
}

.home-actions .btn {
  width: 100%;
  max-width: 320px;
}

.home-player {
  font-size: var(--fs-xs);
  color: var(--c-text-muted);
  text-align: center;
  min-height: var(--fs-xs);
  padding-block-end: var(--sp-2);
}

/* ── How-to-play screen ─────────────────────────── */
#screen-howto {
  align-items: center;
  justify-content: center;
}

.howto-inner {
  display: flex;
  flex-direction: column;
  gap: var(--sp-5);
  padding: var(--sp-8);
  max-width: 420px;
  width: 100%;
}

.howto-title {
  font-size: var(--fs-xl);
  color: var(--c-accent);
  text-align: center;
}

.howto-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  padding-inline-start: var(--sp-5);
}

.howto-list li {
  font-size: var(--fs-sm);
  color: var(--c-text);
  line-height: var(--lh-base);
}

.howto-demo {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-3);
  background-color: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-lg);
  padding: var(--sp-5);
}

.demo-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--sp-2);
}

.demo-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  font-size: var(--fs-xl);
  color: var(--c-accent);
  transform: rotate(var(--rot, 0deg));
  background-color: var(--c-surface-alt);
  border-radius: var(--r-sm);
  border: 1px solid var(--c-border);
}

.demo-caption {
  font-size: var(--fs-xs);
  color: var(--c-text-muted);
  text-align: center;
}

/* ── Level select screen ────────────────────────── */
#screen-levels {
  overflow-y: auto;
}

.levels-header {
  padding: var(--sp-6) var(--sp-6) var(--sp-4);
  text-align: center;
}

.levels-title {
  font-size: var(--fs-xl);
  color: var(--c-text);
}

.levels-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
  gap: var(--sp-3);
  padding: var(--sp-4) var(--sp-6) var(--sp-10);
}

.level-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--sp-1);
  aspect-ratio: 1;
  border-radius: var(--r-md);
  border: 2px solid var(--c-border);
  background-color: var(--c-surface);
  font-family: inherit;
  cursor: pointer;
  transition:
    background-color var(--dur-fast) var(--ease-out),
    border-color     var(--dur-fast) var(--ease-out),
    transform        var(--dur-fast) var(--ease-out);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  min-height: 72px;
}

.level-btn:active { transform: scale(0.94); }
.level-btn:focus-visible { outline: 3px solid var(--c-accent); }

.level-btn--unlocked {
  background-color: var(--c-surface);
  border-color: var(--c-border);
}

.level-btn--completed {
  background-color: var(--c-solved-soft);
  border-color: var(--c-solved);
}

.level-btn--locked {
  background-color: var(--c-surface-alt);
  border-color: transparent;
  opacity: 0.5;
  cursor: not-allowed;
}

.level-btn--current {
  border-color: var(--c-accent);
  box-shadow: 0 0 0 3px var(--c-accent-soft);
}

.level-num {
  font-size: var(--fs-lg);
  font-weight: var(--fw-bold);
  color: var(--c-text);
  line-height: 1;
}

.level-badge {
  font-size: 0.65rem;
  color: var(--c-text-muted);
}

.level-btn--completed .level-num { color: var(--c-solved); }
.level-btn--completed .level-badge { color: var(--c-solved); }
.level-btn--locked .level-num { color: var(--c-text-muted); }

/* ── Leaderboard screen ─────────────────────────── */
#screen-leaderboard {
  overflow-y: auto;
}

.lb-header {
  padding: var(--sp-6) var(--sp-6) var(--sp-4);
  text-align: center;
}

.lb-title {
  font-size: var(--fs-xl);
  color: var(--c-text);
}

.lb-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-2);
  padding: var(--sp-2) var(--sp-5) var(--sp-10);
}

.lb-entry {
  display: grid;
  grid-template-columns: 36px 1fr auto;
  align-items: center;
  gap: var(--sp-3);
  background-color: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  padding: var(--sp-3) var(--sp-4);
  box-shadow: var(--shadow-sm);
}

.lb-entry--me {
  border-color: var(--c-accent);
  background-color: var(--c-accent-soft);
}

.lb-rank {
  font-size: var(--fs-sm);
  font-weight: var(--fw-bold);
  color: var(--c-text-muted);
  text-align: center;
  font-variant-numeric: tabular-nums;
}

.lb-rank--gold   { color: #c9a227; }
.lb-rank--silver { color: #8a8a8a; }
.lb-rank--bronze { color: #a0522d; }

.lb-name {
  font-size: var(--fs-sm);
  font-weight: var(--fw-medium);
  color: var(--c-text);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lb-score {
  font-size: var(--fs-md);
  font-weight: var(--fw-bold);
  color: var(--c-score);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.lb-loading, .lb-empty {
  text-align: center;
  padding: var(--sp-10);
  color: var(--c-text-muted);
  font-size: var(--fs-sm);
}