:root {
  --bg: #000;
  --surface: #111;
  --surface-hover: #1a1a1a;
  --text: #e8e8e8;
  --text-muted: #666;
  --front-color: #5ec4d4;
  --back-color: #d4a85e;
  --know-color: #4a9;
  --dont-know-color: #555;
  --accent: #5ec4d4;
  --radius: 12px;
}

*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  height: 100%;
  background: var(--bg);
}

body {
  min-height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;
  padding: env(safe-area-inset-top) env(safe-area-inset-right)
           env(safe-area-inset-bottom) env(safe-area-inset-left);
}

/* --- Screens --- */

.screen {
  display: none;
  flex-direction: column;
  min-height: 100dvh;
  padding: 2rem 1.5rem;
}

.screen.active {
  display: flex;
}

/* --- Deck selection --- */

#screen-decks {
  align-items: center;
  overflow-y: auto;
  padding-bottom: 4rem;
}

.app-header {
  text-align: center;
  padding: 1rem 0 2rem;
}

.app-header h1 {
  font-size: 1.8rem;
  font-weight: 300;
  letter-spacing: 0.1em;
  color: var(--accent);
}

.subtitle {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 0.3rem;
}

/* Footer */

.app-footer {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid #222;
  width: 100%;
  max-width: 500px;
  text-align: center;
}

.footer-links {
  font-size: 0.85rem;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.6rem;
}

.footer-links a,
.footer-link-btn {
  color: var(--accent);
  text-decoration: none;
  background: none;
  border: none;
  font-size: inherit;
  cursor: pointer;
  padding: 0.25rem 0;
}

.footer-links a:hover,
.footer-link-btn:hover {
  text-decoration: underline;
}

.footer-sep {
  color: var(--text-muted);
}

/* Corner "About" button on the deck screen */

.corner-btn {
  position: absolute;
  top: calc(env(safe-area-inset-top, 0px) + 1rem);
  right: calc(env(safe-area-inset-right, 0px) + 1rem);
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.85rem;
  cursor: pointer;
  padding: 0.5rem;
  z-index: 10;
}

.corner-btn:hover {
  color: var(--accent);
}

/* About screen */

#screen-about {
  align-items: center;
  overflow-y: auto;
  padding: 3.5rem 1.5rem 3rem;
}

.about-content {
  max-width: 500px;
  width: 100%;
  color: var(--text-muted);
  line-height: 1.6;
  font-size: 0.9rem;
}

.about-content h2 {
  color: var(--text);
  font-size: 1.4rem;
  font-weight: 400;
  margin-bottom: 1rem;
  text-align: center;
}

.about-content h3 {
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 2rem;
  margin-bottom: 0.6rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid #222;
}

.about-content h4 {
  color: var(--text);
  font-size: 0.85rem;
  font-weight: 500;
  margin-top: 1rem;
  margin-bottom: 0.4rem;
}

.about-content p {
  margin-bottom: 0.8rem;
}

.about-content strong {
  color: var(--text);
  font-weight: 500;
}

.about-content ul,
.about-content ol {
  margin-bottom: 0.8rem;
  padding-left: 1.2rem;
}

.about-content li {
  margin-bottom: 0.4rem;
}

.about-content a {
  color: var(--accent);
  text-decoration: none;
}

.about-content a:hover {
  text-decoration: underline;
}

.credits-intro {
  font-style: italic;
}

/* Deck filters */

.deck-filters {
  display: flex;
  gap: 0.5rem;
  width: 100%;
  max-width: 500px;
  overflow-x: auto;
  padding-bottom: 0.5rem;
  -webkit-overflow-scrolling: touch;
}

.deck-filters::-webkit-scrollbar { display: none; }

.filter-chip {
  flex-shrink: 0;
  padding: 0.45rem 1rem;
  border: 1px solid #333;
  border-radius: 99px;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.85rem;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}

.filter-chip.active {
  background: var(--accent);
  color: #000;
  border-color: var(--accent);
}

.filter-chip:not(.active):hover {
  border-color: #555;
  color: var(--text);
}

/* Deck grid */

.deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(155px, 1fr));
  gap: 0.6rem;
  width: 100%;
  max-width: 500px;
  padding-top: 0.8rem;
}

.deck-tile {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 1rem;
  min-height: 90px;
  background: var(--surface);
  border: none;
  border-radius: var(--radius);
  color: var(--text);
  font-size: 0.9rem;
  text-align: left;
  cursor: pointer;
  transition: background 0.15s;
}

.deck-tile:hover, .deck-tile:active {
  background: var(--surface-hover);
}

.deck-tile-name {
  font-weight: 500;
  line-height: 1.3;
}

.deck-tile-count {
  color: var(--text-muted);
  font-size: 0.75rem;
  margin-top: 0.5rem;
}

/* --- Mode selection --- */

#screen-mode {
  align-items: center;
  justify-content: center;
  position: relative;
}

.back-btn {
  position: absolute;
  top: calc(env(safe-area-inset-top, 0px) + 1rem);
  left: calc(env(safe-area-inset-left, 0px) + 1rem);
  background: none;
  border: none;
  color: var(--accent);
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.5rem;
}

#mode-deck-name {
  font-size: 1.4rem;
  font-weight: 400;
  margin-bottom: 0.3rem;
  text-align: center;
}

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

.mode-buttons {
  display: flex;
  gap: 1rem;
  margin-top: 2rem;
}

.mode-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1.5rem 2rem;
  background: var(--surface);
  border: none;
  border-radius: var(--radius);
  color: var(--text);
  cursor: pointer;
  transition: background 0.15s;
  min-width: 130px;
}

.mode-btn:hover, .mode-btn:active {
  background: var(--surface-hover);
}

.mode-icon {
  font-size: 2rem;
  margin-bottom: 0.5rem;
  color: var(--accent);
}

.mode-label {
  font-size: 1rem;
  font-weight: 500;
}

.mode-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 0.2rem;
}

/* --- Field config (mode screen) --- */

.field-config {
  width: 100%;
  max-width: 340px;
  margin-top: 1.5rem;
}

.field-config-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.field-config-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.6rem 0;
}

.field-config-info {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  min-width: 0;
}

.field-config-label {
  font-size: 0.9rem;
}

.field-config-sample {
  font-size: 0.85rem;
  color: var(--text-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 120px;
}

.field-config-toggle {
  flex-shrink: 0;
  padding: 0.3rem 0.75rem;
  border: none;
  border-radius: 99px;
  font-size: 0.75rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s;
  min-width: 60px;
  text-align: center;
}

.field-config-toggle.front {
  background: var(--front-color);
  color: #000;
}

.field-config-toggle.back {
  background: var(--back-color);
  color: #000;
}

.field-config-toggle.hidden {
  background: #333;
  color: var(--text-muted);
}

/* --- Ambient speed selector --- */

.speed-selector {
  width: 100%;
  max-width: 340px;
  margin-top: 1.5rem;
}

.speed-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.speed-chips {
  display: flex;
  gap: 0.4rem;
}

.speed-chip {
  flex: 1;
  padding: 0.45rem 0.4rem;
  border: 1px solid #333;
  border-radius: 99px;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.75rem;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  white-space: nowrap;
}

.speed-chip.active {
  background: var(--accent);
  color: #000;
  border-color: var(--accent);
}

.speed-chip:not(.active):hover {
  border-color: #555;
  color: var(--text);
}

/* --- Card display --- */

.card-display {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  flex: 1;
  width: 100%;
  gap: 1rem;
}

.field-group {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.3rem;
}

.field-group.front .field-value { color: var(--front-color); }
.field-group.back .field-value { color: var(--back-color); }

.field-value {
  font-size: clamp(1.8rem, 8vw, 4rem);
  font-weight: 300;
  line-height: 1.3;
  text-align: center;
  word-break: break-word;
}

.field-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Reveal state: front fields shrink to give emphasis to back */
.card-display.reveal .field-group.front .field-value {
  font-size: clamp(1.2rem, 5vw, 2rem);
  opacity: 0.5;
}

/* --- Ambient mode --- */

#screen-ambient {
  justify-content: center;
  align-items: center;
  cursor: pointer;
}

#ambient-card {
  transition: opacity 0.3s ease;
}

/* Landscape (phone-in-landscape "StandBy-style" nightstand use):
 * grow the text to fill the short dimension, tighten padding so
 * nothing gets clipped. Only kicks in when the viewport is short,
 * so desktop browsers are unaffected. */
@media (orientation: landscape) and (max-height: 600px) {
  #screen-ambient {
    padding: 0.8rem 2rem;
  }

  #ambient-card .field-value {
    font-size: clamp(2rem, 22vh, 7rem);
    line-height: 1.1;
  }

  #ambient-hint {
    font-size: 0.65rem;
    bottom: calc(env(safe-area-inset-bottom, 0px) + 0.5rem);
  }
}

/* --- Flashcard mode --- */

#screen-flashcard {
  align-items: center;
}

.progress-bar {
  width: 100%;
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-muted);
  padding: 0.5rem 0;
}

.actions {
  display: flex;
  gap: 1rem;
  padding: 1.5rem 0;
  width: 100%;
  max-width: 400px;
}

.actions.hidden {
  display: none;
}

.action-btn {
  flex: 1;
  padding: 1rem;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
  color: #fff;
}

.action-btn:active {
  transform: scale(0.97);
}

.action-btn.know { background: var(--know-color); }
.action-btn.dont-know { background: var(--dont-know-color); }
.action-btn.next { background: var(--surface); color: var(--text); }

.hint {
  position: fixed;
  bottom: calc(env(safe-area-inset-bottom, 0px) + 1.5rem);
  left: 0;
  right: 0;
  text-align: center;
  font-size: 0.75rem;
  color: var(--text-muted);
  pointer-events: none;
}

/* --- Score screen --- */

#screen-score {
  align-items: center;
  justify-content: center;
  gap: 1.5rem;
}

.score-title {
  font-size: 1.4rem;
  font-weight: 400;
}

.score-ring {
  width: 160px;
  height: 160px;
  position: relative;
}

.score-ring svg {
  width: 100%;
  height: 100%;
}

.score-pct {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
  font-weight: 300;
}

.score-text {
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* --- Animation --- */

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.card-display .field-group {
  animation: fadeIn 0.3s ease;
}