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

:root {
  --bg: #000;
  --text: #f0f0f0;
  --text-muted: #999;
  --accent: #6c8cff;
  --success: #4caf50;
  --error: #e53935;
  --card-bg: #1a1a1a;
  --overlay-bg: rgba(0, 0, 0, 0.7);
  --panel-bg: #1e1e1e;
  --border: #333;
  --radius: 16px;
  --flip-duration: 550ms;
  --swipe-duration: 340ms;
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}

html {
  height: 100%;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  height: 100%;
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
}

#app {
  display: flex;
  flex-direction: column;
  height: 100%;
  height: 100dvh;
  max-width: 900px;
  margin: 0 auto;
  overflow: hidden;
  padding:
    env(safe-area-inset-top)
    env(safe-area-inset-right)
    env(safe-area-inset-bottom)
    env(safe-area-inset-left);
}

/* Topbar */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  flex-shrink: 0;
}

.topbar__title {
  font-size: 1.25rem;
  font-weight: 600;
  letter-spacing: -0.02em;
}

.topbar__status {
  font-size: 0.95rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

.topbar__settings {
  background: none;
  border: none;
  color: var(--text);
  cursor: pointer;
  padding: 8px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.topbar__settings:hover {
  background: rgba(255, 255, 255, 0.08);
}

.topbar__settings-icon {
  display: block;
  width: 24px;
  height: 24px;
}

/* Main */
.main {
  flex: 1 1 0;
  display: flex;
  flex-direction: column;
  min-height: 0;
  overflow: hidden;
  position: relative;
}

.view {
  display: none;
  flex: 1 1 0;
  flex-direction: column;
  min-height: 0;
}

.view--active {
  display: flex;
}

#quiz-view {
  overflow-x: hidden;
  overflow-y: scroll;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior-y: contain;
  touch-action: pan-y;
}

/* Flashcard */
.card-viewport {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 8px 16px;
  touch-action: manipulation;
  outline: none;
  position: relative;
  min-height: 0;
}

.card-viewport:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
  border-radius: var(--radius);
}

.card-stack {
  position: relative;
  width: 100%;
  max-width: 100%;
  aspect-ratio: 3 / 4;
  max-height: calc(100dvh - 160px);
}

.card {
  position: absolute;
  inset: 0;
  will-change: transform, opacity;
}

.card--next {
  z-index: 1;
  transform: scale(0.95);
  opacity: 0;
  pointer-events: none;
  transition: transform var(--swipe-duration) ease, opacity var(--swipe-duration) ease;
}

.card--next.card--revealing {
  transform: scale(1);
  opacity: 1;
}

.card--current {
  z-index: 2;
  transition: transform var(--swipe-duration) ease, opacity var(--swipe-duration) ease;
}

.card--current.card--dragging {
  transition: none;
}

.card--current.card--swipe-left {
  transform: translateX(-120%) rotate(-8deg);
  opacity: 0;
}

.card--current.card--swipe-right {
  transform: translateX(120%) rotate(8deg);
  opacity: 0;
}

.card--current.card--snap-back {
  transition: transform var(--swipe-duration) ease;
  transform: translateX(0) rotate(0);
}

.card--no-transition {
  transition: none !important;
}

.card__inner {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform var(--flip-duration) ease;
  border-radius: var(--radius);
}

.card--flipped .card__inner {
  transform: rotateY(180deg);
}

.card__face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card-bg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.card__face--front {
  padding: 0;
}

.card__face--back {
  transform: rotateY(180deg);
  padding: 24px;
  text-align: center;
  gap: 12px;
}

.card__image {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  border-radius: var(--radius);
}

.card__movement {
  display: inline-block;
  background: rgba(108, 140, 255, 0.2);
  color: var(--accent);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 500;
}

.card__title {
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.3;
}

.card__artist {
  font-size: 1rem;
  color: var(--text);
}

/* Swipe hints */
.swipe-hints {
  display: flex;
  justify-content: space-between;
  padding: 12px 24px 16px;
  flex-shrink: 0;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.swipe-hints__btn {
  background: none;
  border: none;
  padding: 0;
  font: inherit;
  color: inherit;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.swipe-hints__btn:hover {
  color: var(--text);
}

.swipe-hints__left {
  opacity: 0.7;
}

.swipe-hints__right {
  opacity: 0.7;
}

/* Quiz */
.quiz {
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  width: 100%;
  padding: 8px 16px max(24px, env(safe-area-inset-bottom));
}

.quiz__image-wrap {
  width: 100%;
  aspect-ratio: 4 / 3;
  max-height: 40vh;
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card-bg);
  flex-shrink: 0;
}

.quiz__image {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.quiz__question {
  font-size: 1.1rem;
  font-weight: 500;
  margin: 16px 0;
  text-align: center;
}

.quiz__options {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.quiz__option {
  width: 100%;
  padding: 14px 16px;
  background: var(--card-bg);
  border: 2px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  font-family: inherit;
  font-size: 1rem;
  text-align: left;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.quiz__option:hover:not(:disabled) {
  border-color: var(--accent);
}

.quiz__option:disabled {
  cursor: default;
}

.quiz__option--correct {
  border-color: var(--success);
  background: rgba(76, 175, 80, 0.15);
}

.quiz__option--wrong {
  border-color: var(--error);
  background: rgba(229, 57, 53, 0.15);
}

.quiz__feedback {
  margin-top: 16px;
  text-align: center;
  font-size: 0.95rem;
  min-height: 1.4em;
  color: var(--text-muted);
}

.quiz__feedback--correct {
  color: var(--success);
}

.quiz__feedback--wrong {
  color: var(--error);
}

.quiz__next {
  margin-top: 16px;
  align-self: center;
}

/* Completion */
.completion {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 24px;
  padding: 24px;
}

.completion__title {
  font-size: 1.75rem;
  font-weight: 600;
  text-align: center;
}

/* Buttons */
.btn {
  padding: 12px 24px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 12px;
  font-family: inherit;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: opacity 0.15s;
}

.btn:hover {
  opacity: 0.9;
}

.btn--secondary {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  width: 100%;
}

.btn--secondary:hover {
  background: rgba(255, 255, 255, 0.05);
}

/* Confetti */
.confetti-canvas {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 100;
}

/* Settings overlay */
.settings-overlay {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  visibility: hidden;
  opacity: 0;
  transition: visibility 0.25s, opacity 0.25s;
}

.settings-overlay[aria-hidden="false"] {
  visibility: visible;
  opacity: 1;
}

.settings-backdrop {
  position: absolute;
  inset: 0;
  background: var(--overlay-bg);
}

.settings-panel {
  position: relative;
  width: 100%;
  max-width: 900px;
  max-height: 85dvh;
  background: var(--panel-bg);
  border-radius: 20px 20px 0 0;
  overflow-y: auto;
  transform: translateY(100%);
  transition: transform 0.3s ease;
  padding-bottom: env(safe-area-inset-bottom);
}

.settings-overlay[aria-hidden="false"] .settings-panel {
  transform: translateY(0);
}

.settings-panel__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 20px 12px;
  border-bottom: 1px solid var(--border);
}

.settings-panel__title {
  font-size: 1.2rem;
  font-weight: 600;
}

.settings-panel__close {
  background: none;
  border: none;
  color: var(--text);
  font-size: 1.75rem;
  line-height: 1;
  cursor: pointer;
  padding: 4px 8px;
}

.settings-panel__body {
  padding: 16px 20px 24px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.settings-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.settings-group__label,
.settings-group label {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}

.settings-group select {
  padding: 10px 12px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 1rem;
}

.tab-group {
  display: flex;
  gap: 8px;
}

.tab {
  flex: 1;
  padding: 10px 16px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 0.95rem;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}

.tab--active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

@media (min-width: 600px) {
  .settings-overlay {
    align-items: center;
  }

  .settings-panel {
    border-radius: 20px;
    max-width: 420px;
    margin: 16px;
  }

  .settings-overlay[aria-hidden="false"] .settings-panel {
    transform: translateY(0);
  }
}