/* ── Reset & Base ─────────────────────────────────────────────────────────── */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg-primary:    #0d0e1a;
  --bg-secondary:  #13152a;
  --bg-card:       #1a1d35;
  --bg-card-hover: #1f2240;
  --accent-purple: #7c6af7;
  --accent-blue:   #4a9eff;
  --accent-teal:   #2dd4bf;
  --text-primary:  #e8e9f5;
  --text-secondary:#9899b8;
  --text-muted:    #5c5e7a;
  --border:        #252748;
  --border-active: #7c6af7;

  --quality-optimal: #4ade80;
  --quality-good:    #a3e635;
  --quality-fair:    #facc15;
  --quality-short:   #f87171;

  --phase-light: #7c9fcf;
  --phase-deep:  #3a5fa0;
  --phase-rem:   #9b7fdb;

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;

  --font: 'Segoe UI', 'Noto Sans JP', system-ui, sans-serif;
}

html, body {
  height: 100%;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.6;
}

/* ── Layout ──────────────────────────────────────────────────────────────── */
.page {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2rem 1rem 4rem;
}

.container {
  width: 100%;
  max-width: 640px;
}

/* ── Header ──────────────────────────────────────────────────────────────── */
.header {
  text-align: center;
  margin-bottom: 2rem;
  position: relative;
}

.header-top {
  display: flex;
  justify-content: flex-end;
  margin-bottom: 1rem;
}

.lang-toggle {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 0.3rem 0.8rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  transition: all 0.2s;
}

.lang-toggle:hover {
  border-color: var(--accent-purple);
  color: var(--text-primary);
}

.moon-icon {
  font-size: 2.5rem;
  line-height: 1;
  margin-bottom: 0.5rem;
  display: block;
}

.app-title {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.3rem;
}

.app-subtitle {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

/* ── Card ────────────────────────────────────────────────────────────────── */
.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1.25rem;
}

/* ── Tabs ────────────────────────────────────────────────────────────────── */
.tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

.tab-btn {
  flex: 1;
  padding: 0.65rem 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
}

.tab-btn:hover {
  border-color: var(--accent-purple);
  color: var(--text-primary);
}

.tab-btn.active {
  background: var(--accent-purple);
  border-color: var(--accent-purple);
  color: #fff;
  font-weight: 600;
}

/* ── Form ────────────────────────────────────────────────────────────────── */
.panel {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.panel.hidden {
  display: none;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.field label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.time-row {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

input[type="time"] {
  flex: 1;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 1.5rem;
  font-weight: 600;
  padding: 0.5rem 0.75rem;
  outline: none;
  transition: border-color 0.2s;
  /* Browser-specific */
  color-scheme: dark;
}

input[type="time"]:focus {
  border-color: var(--accent-purple);
}

.btn-now {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  padding: 0.5rem 0.9rem;
  font-size: 0.8rem;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.2s;
}

.btn-now:hover {
  border-color: var(--accent-purple);
  color: var(--text-primary);
}

/* ── Slider ──────────────────────────────────────────────────────────────── */
.slider-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

input[type="range"] {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 4px;
  border-radius: 2px;
  background: var(--border);
  outline: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent-purple);
  cursor: pointer;
}

input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent-purple);
  cursor: pointer;
  border: none;
}

.slider-value {
  min-width: 2.5rem;
  text-align: right;
  font-size: 0.9rem;
  color: var(--text-primary);
  font-weight: 600;
}

/* ── Calculate button ────────────────────────────────────────────────────── */
.btn-calculate {
  width: 100%;
  padding: 0.9rem;
  background: linear-gradient(135deg, var(--accent-purple), var(--accent-blue));
  border: none;
  border-radius: var(--radius-md);
  color: #fff;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  letter-spacing: 0.04em;
  transition: opacity 0.2s, transform 0.1s;
}

.btn-calculate:hover {
  opacity: 0.9;
}

.btn-calculate:active {
  transform: scale(0.98);
}

/* ── Results ─────────────────────────────────────────────────────────────── */
.results-section {
  margin-top: 0.5rem;
}

.results-section.hidden {
  display: none;
}

.results-title {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.75rem;
}

.results-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

/* ── Result Card ─────────────────────────────────────────────────────────── */
.result-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 1rem 1.1rem;
  transition: background 0.2s, border-color 0.2s;
  border-left: 3px solid var(--border);
}

.result-card:hover {
  background: var(--bg-card-hover);
}

.result-card.quality-optimal {
  border-left-color: var(--quality-optimal);
}

.result-card.quality-good {
  border-left-color: var(--quality-good);
}

.result-card.quality-fair {
  border-left-color: var(--quality-fair);
}

.result-card.quality-short {
  border-left-color: var(--quality-short);
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.card-time {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  line-height: 1;
}

.card-meta {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.cycles-badge,
.hours-badge {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.2rem 0.6rem;
  font-size: 0.78rem;
  color: var(--text-secondary);
  font-weight: 500;
  white-space: nowrap;
}

.quality-badge {
  border-radius: 999px;
  padding: 0.2rem 0.6rem;
  font-size: 0.78rem;
  font-weight: 700;
  white-space: nowrap;
}

.quality-badge.quality-optimal {
  background: rgba(74, 222, 128, 0.15);
  color: var(--quality-optimal);
}

.quality-badge.quality-good {
  background: rgba(163, 230, 53, 0.15);
  color: var(--quality-good);
}

.quality-badge.quality-fair {
  background: rgba(250, 204, 21, 0.15);
  color: var(--quality-fair);
}

.quality-badge.quality-short {
  background: rgba(248, 113, 113, 0.15);
  color: var(--quality-short);
}

.card-explain {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

/* ── Sleep Phase Diagram ─────────────────────────────────────────────────── */
.sleep-diagram {
  margin-top: 0.4rem;
}

.diagram-track {
  display: flex;
  height: 8px;
  border-radius: 4px;
  overflow: hidden;
  gap: 1px;
  background: var(--bg-secondary);
}

.phase {
  border-radius: 1px;
  transition: opacity 0.2s;
}

.phase-light {
  background: var(--phase-light);
}

.phase-deep {
  background: var(--phase-deep);
}

.phase-rem {
  background: var(--phase-rem);
}

/* ── Legend ──────────────────────────────────────────────────────────────── */
.legend-row {
  display: flex;
  gap: 1.2rem;
  margin-top: 0.5rem;
  font-size: 0.75rem;
  color: var(--text-muted);
  flex-wrap: wrap;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.legend-dot {
  width: 10px;
  height: 10px;
  border-radius: 2px;
  flex-shrink: 0;
}

.legend-dot.light { background: var(--phase-light); }
.legend-dot.deep  { background: var(--phase-deep); }
.legend-dot.rem   { background: var(--phase-rem); }

/* ── Footer ──────────────────────────────────────────────────────────────── */
.footer {
  margin-top: 2rem;
  text-align: center;
}

.footer-text {
  font-size: 0.78rem;
  color: var(--text-muted);
  max-width: 480px;
  margin: 0 auto;
  line-height: 1.7;
}

/* ── Hidden utility ──────────────────────────────────────────────────────── */
.hidden {
  display: none !important;
}

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width: 480px) {
  .app-title {
    font-size: 1.3rem;
  }

  .card-time {
    font-size: 1.7rem;
  }

  .tabs {
    flex-direction: column;
  }

  .card-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .card-meta {
    justify-content: flex-start;
  }
}