.study-open { overflow: hidden; }
.study-sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.study-error { padding: 16px; border: 1px solid var(--danger); border-radius: 12px; color: var(--danger); background: var(--surface); overflow-wrap: anywhere; }
.study-dialog { width: min(760px, calc(100% - 24px)); max-height: calc(100dvh - 32px); padding: 32px; border: 1px solid var(--line); border-radius: var(--radius); color: var(--ink); background: var(--canvas); box-shadow: var(--shadow); overscroll-behavior: contain; }
.study-dialog::backdrop { background: #100a23b3; }
.study-topline, .study-progress-label, .study-session-footer, .saved-deck-top { display: flex; align-items: center; justify-content: space-between; gap: 16px; }
.study-topline .eyebrow { font-size: 11px; }
.study-close { flex-shrink: 0; min-width: 44px; min-height: 44px; padding: 0; font-size: 24px; }
.study-dialog h2 { font-size: clamp(24px, 5vw, 36px); margin: 16px 0 24px; overflow-wrap: anywhere; }
.study-progress-label { color: var(--subtle); font-size: 13px; font-variant-numeric: tabular-nums; }
#study-progress { appearance: none; display: block; width: 100%; height: 6px; border: 0; border-radius: 8px; overflow: hidden; margin: 12px 0 24px; background: var(--line); accent-color: var(--accent); }
#study-progress::-webkit-progress-bar { background: var(--line); }
#study-progress::-webkit-progress-value { background: var(--accent); transition: width .2s; }
#study-progress::-moz-progress-bar { background: var(--accent); }
.study-card { perspective: 1400px; cursor: pointer; touch-action: pan-y pinch-zoom; outline-offset: 6px; border-radius: 20px; }
.study-card-inner { display: grid; transform-style: preserve-3d; transition: transform .25s ease; }
.study-card.is-flipped .study-card-inner { transform: rotateY(180deg); }
.study-face { grid-area: 1 / 1; min-width: 0; min-height: 280px; display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 32px; border: 1px solid var(--line); border-radius: 20px; background: var(--surface); backface-visibility: hidden; -webkit-backface-visibility: hidden; text-align: center; box-shadow: var(--shadow-card); }
.study-face p { width: 100%; margin: 24px 0; white-space: pre-wrap; overflow-wrap: anywhere; font-size: clamp(19px, 3.4vw, 26px); line-height: 1.6; }
.study-back { transform: rotateY(180deg); background: var(--tint); }
.study-card-hint { color: var(--subtle); font-size: 13px; margin-top: auto; }
.study-face > .eyebrow { margin-bottom: auto; }
.study-shortcuts { margin: 16px 0; color: var(--subtle); text-align: center; font-size: 12px; line-height: 1.8; }
#study-flip { width: 100%; min-height: 56px; }
.study-dialog kbd { font: inherit; font-size: 12px; opacity: .85; }
#study-flip kbd { margin-left: 16px; }
.study-ratings { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 8px; }
.study-rating { display: flex; flex-direction: column; gap: 4px; min-width: 0; min-height: 72px; padding: 12px 4px; }
.study-rating small { font-size: 12px; font-weight: 400; color: var(--subtle); }
.study-rating kbd { display: inline-grid; place-items: center; width: 18px; height: 18px; border: 1px solid var(--line); border-radius: 5px; margin-right: 2px; }
.study-rating-again { color: var(--danger) !important; }
.study-rating-good { background: var(--tint) !important; border-color: var(--accent) !important; color: var(--accent) !important; }
.study-rating-easy { color: var(--success) !important; }
.study-session-footer { margin-top: 24px; font-size: 12px; color: var(--subtle); }
.study-session-footer button { min-height: 44px; flex-shrink: 0; font-size: 13px; }
.study-summary { padding: 12px 0; text-align: center; }
.study-summary-mark { display: inline-grid; place-items: center; width: 64px; height: 64px; border-radius: 20px; background: var(--success-tint); color: var(--success); margin-bottom: 24px; }
.study-summary-mark .icon { width: 32px; height: 32px; }
.study-summary h3 { font-size: clamp(24px, 5vw, 32px); margin-bottom: 12px; }
.study-summary p { color: var(--subtle); }
.study-summary-stats, .deck-stats { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin: 32px 0; }
.study-summary-stats > div { padding: 16px 8px; border-radius: 16px; background: var(--surface); border: 1px solid var(--line); }
.study-summary-stats strong, .deck-stats strong { display: block; font-size: 32px; color: var(--accent); font-variant-numeric: tabular-nums; }
.study-summary-stats span, .deck-stats span { color: var(--subtle); font-size: 13px; }
.study-breakdown, .study-summary-actions { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; }
.study-breakdown { font-size: 13px; color: var(--subtle); }
.study-summary-actions { margin-top: 24px; }
.decks-main { max-width: 1120px; padding-top: 56px; padding-bottom: 64px; }
.decks-heading { display: flex; justify-content: space-between; align-items: center; gap: 24px; }
.decks-heading h1 { font-size: clamp(36px, 6vw, 56px); margin: 16px 0; }
.decks-heading p { max-width: 560px; color: var(--subtle); }
.decks-heading > .btn { flex-shrink: 0; }
.deck-stats .box { padding: 24px; }
.deck-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; margin: 24px 0; }
.saved-deck { min-width: 0; display: flex; flex-direction: column; align-items: flex-start; }
.saved-deck h2 { font-size: 24px; line-height: 1.35; overflow-wrap: anywhere; margin: 24px 0 12px; }
.saved-deck-top { width: 100%; flex-wrap: wrap; }
.saved-deck-total { font-size: 13px; }
.saved-deck-next { margin-bottom: 24px; font-size: 14px; }
.saved-deck button { margin-top: auto; min-height: 48px; }
.decks-empty { text-align: center; padding: 56px 24px; margin: 24px 0; }
.decks-empty h2 { font-size: 28px; margin: 16px 0; }
.decks-empty p { color: var(--subtle); }
.decks-privacy { color: var(--subtle); font-size: 13px; }
.study-dialog button, .saved-deck button { cursor: pointer; transition: background .18s, border-color .18s; }
.study-dialog button:active, .saved-deck button:active { filter: brightness(.92); }
.study-dialog :focus-visible, .decks-page :focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }
.decks-page .site-nav a, .decks-page .theme-toggle { min-height: 44px; }
@media (max-width: 600px) {
  .home-page .site-nav .how-link { display: none; }
  .study-dialog { padding: 20px 16px max(20px, env(safe-area-inset-bottom)); max-height: calc(100dvh - 16px); }
  .study-topline .eyebrow { max-width: 220px; line-height: 1.6; }
  .study-face { padding: 24px 20px; min-height: 248px; }
  .study-ratings { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .study-rating { min-height: 64px; }
  .study-summary-stats, .deck-stats { gap: 8px; }
  .study-summary-stats span { font-size: 12px; }
  .study-session-footer { align-items: flex-start; }
  .decks-main { padding-top: 32px; }
  .decks-heading { display: block; }
  .deck-stats .box { padding: 16px 12px; }
  .deck-list { grid-template-columns: 1fr; gap: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  .study-card-inner, #study-progress::-webkit-progress-value, .study-dialog button, .saved-deck button { transition: none; }
}