/* Recall — flashcards PWA */
:root{
  --bg:#0f1117; --bg2:#171a23; --bg3:#1f2330; --line:#2a2f3f;
  --text:#e8eaf2; --muted:#9aa1b5; --faint:#6b7288;
  --accent:#7c6cff; --accent2:#4ecdc4; --danger:#ff6b6b; --warn:#ffb84d; --ok:#5dd39e;
  --grad:linear-gradient(135deg,#7c6cff 0%,#4ecdc4 100%);
  --radius:16px; --shadow:0 8px 32px rgba(0,0,0,.35);
  --safe-b:env(safe-area-inset-bottom,0px);
}
*{margin:0;padding:0;box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html{font-size:16px}
body{background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Inter,Roboto,sans-serif;min-height:100dvh}
button{font-family:inherit;cursor:pointer;border:none;background:none;color:inherit}
input,textarea{font-family:inherit;font-size:1rem;color:var(--text);background:var(--bg3);border:1px solid var(--line);border-radius:12px;padding:.8rem 1rem;width:100%;outline:none}
input:focus,textarea:focus{border-color:var(--accent)}
textarea{resize:vertical;min-height:90px}
a{color:var(--accent2);text-decoration:none}

.boot{display:flex;align-items:center;justify-content:center;height:100dvh}
.logo-mark{width:72px;height:72px;border-radius:20px;background:var(--grad);display:flex;align-items:center;justify-content:center;font-size:2.2rem;font-weight:800;color:#fff;animation:pulse 1.2s ease infinite}
@keyframes pulse{50%{transform:scale(1.08);opacity:.85}}

/* layout */
.shell{max-width:860px;margin:0 auto;padding:0 1rem calc(90px + var(--safe-b))}
.topbar{display:flex;align-items:center;gap:.75rem;padding:1rem 0;position:sticky;top:0;background:linear-gradient(var(--bg) 70%,transparent);z-index:10}
.topbar .logo-mark{width:38px;height:38px;border-radius:11px;font-size:1.2rem;animation:none;cursor:pointer}
.topbar h1{font-size:1.25rem;font-weight:700;flex:1}
.topbar .sub{font-size:.8rem;color:var(--muted)}
.iconbtn{width:38px;height:38px;border-radius:11px;background:var(--bg3);display:flex;align-items:center;justify-content:center;font-size:1.1rem;transition:.15s}
.iconbtn:hover{background:var(--line)}
.back{color:var(--muted);font-size:.9rem;padding:.4rem 0;display:inline-flex;align-items:center;gap:.3rem}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;padding:.8rem 1.4rem;border-radius:12px;font-weight:600;font-size:.95rem;transition:.15s;white-space:nowrap}
.btn-primary{background:var(--grad);color:#fff;box-shadow:0 4px 16px rgba(124,108,255,.35)}
.btn-primary:hover{filter:brightness(1.1)}
.btn-ghost{background:var(--bg3);color:var(--text);border:1px solid var(--line)}
.btn-ghost:hover{border-color:var(--accent)}
.btn-danger{background:rgba(255,107,107,.12);color:var(--danger)}
.btn-sm{padding:.5rem .9rem;font-size:.85rem;border-radius:10px}
.btn-block{width:100%}
.btn:disabled{opacity:.5;cursor:not-allowed}

/* auth */
.auth{max-width:400px;margin:0 auto;padding:12vh 1.2rem 2rem;display:flex;flex-direction:column;gap:1rem}
.auth .logo-mark{align-self:center;animation:none}
.auth h1{text-align:center;font-size:1.7rem}
.auth p.tag{text-align:center;color:var(--muted);margin-bottom:.5rem}
.auth .switch{text-align:center;color:var(--muted);font-size:.9rem}
.field label{display:block;font-size:.8rem;color:var(--muted);margin-bottom:.35rem}

/* cards & grids */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:1rem;margin-top:1rem}
.deck-card{background:var(--bg2);border:1px solid var(--line);border-radius:var(--radius);padding:1.1rem;cursor:pointer;transition:.18s;position:relative;overflow:hidden}
.deck-card:hover{transform:translateY(-3px);border-color:var(--accent);box-shadow:var(--shadow)}
.deck-card::before{content:'';position:absolute;top:0;left:0;right:0;height:3px;background:var(--grad)}
.deck-card h3{font-size:1.05rem;margin-bottom:.3rem}
.deck-card p{font-size:.85rem;color:var(--muted);margin-bottom:.8rem;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.deck-meta{display:flex;gap:.6rem;font-size:.78rem;color:var(--faint);align-items:center;flex-wrap:wrap}
.pill{background:var(--bg3);padding:.2rem .6rem;border-radius:99px}
.pill.due{background:rgba(255,184,77,.15);color:var(--warn)}
.pill.pub{background:rgba(94,211,158,.15);color:var(--ok)}

.empty{text-align:center;padding:3rem 1rem;color:var(--muted)}
.empty .big{font-size:2.6rem;margin-bottom:.6rem}

/* stats strip */
.stats-strip{display:grid;grid-template-columns:repeat(3,1fr);gap:.8rem;margin-top:.5rem}
.stat-box{background:var(--bg2);border:1px solid var(--line);border-radius:var(--radius);padding:.9rem;text-align:center}
.stat-box .num{font-size:1.5rem;font-weight:800;background:var(--grad);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.stat-box .lbl{font-size:.72rem;color:var(--muted);text-transform:uppercase;letter-spacing:.05em}

/* deck detail */
.deck-head{margin:.6rem 0 1rem}
.deck-head h2{font-size:1.5rem;margin-bottom:.25rem}
.deck-head p{color:var(--muted);font-size:.92rem}
.actions{display:flex;gap:.6rem;flex-wrap:wrap;margin:1rem 0}
.card-row{background:var(--bg2);border:1px solid var(--line);border-radius:12px;padding:.9rem 1rem;margin-bottom:.6rem;display:flex;gap:.9rem;align-items:flex-start}
.card-row .txt{flex:1;min-width:0}
.card-row .front{font-weight:600;margin-bottom:.2rem;word-wrap:break-word}
.card-row .backtxt{color:var(--muted);font-size:.88rem;word-wrap:break-word}
.card-row .ops{display:flex;gap:.3rem;flex-shrink:0}
.card-row .ops button{color:var(--faint);font-size:.95rem;padding:.3rem;border-radius:8px}
.card-row .ops button:hover{color:var(--text);background:var(--bg3)}
.srs-tag{font-size:.7rem;color:var(--faint);margin-top:.3rem}

/* study */
.study-wrap{display:flex;flex-direction:column;align-items:center;padding-top:1rem}
.progressbar{width:100%;height:6px;background:var(--bg3);border-radius:99px;overflow:hidden;margin-bottom:1.4rem}
.progressbar>div{height:100%;background:var(--grad);border-radius:99px;transition:width .3s}
.flip-scene{width:100%;max-width:560px;height:340px;perspective:1200px;cursor:pointer}
.flip-card{width:100%;height:100%;position:relative;transform-style:preserve-3d;transition:transform .5s cubic-bezier(.4,.1,.2,1)}
.flip-card.flipped{transform:rotateY(180deg)}
.flip-face{position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;background:var(--bg2);border:1px solid var(--line);border-radius:20px;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:2rem;text-align:center;box-shadow:var(--shadow)}
.flip-face .side-lbl{position:absolute;top:1rem;left:1.2rem;font-size:.72rem;color:var(--faint);text-transform:uppercase;letter-spacing:.1em}
.flip-face .content{font-size:1.35rem;font-weight:600;overflow-wrap:anywhere;max-height:100%;overflow-y:auto}
.flip-face.backface{transform:rotateY(180deg);border-color:var(--accent)}
.hint{color:var(--faint);font-size:.85rem;margin-top:1rem}
.grade-row{display:grid;grid-template-columns:repeat(4,1fr);gap:.6rem;width:100%;max-width:560px;margin-top:1.4rem}
.grade-btn{padding:.9rem .4rem;border-radius:14px;font-weight:700;font-size:.9rem;display:flex;flex-direction:column;gap:.15rem;align-items:center;transition:.15s}
.grade-btn small{font-weight:400;font-size:.68rem;opacity:.75}
.grade-btn:hover{transform:translateY(-2px)}
.g-again{background:rgba(255,107,107,.15);color:var(--danger)}
.g-hard{background:rgba(255,184,77,.15);color:var(--warn)}
.g-good{background:rgba(94,211,158,.15);color:var(--ok)}
.g-easy{background:rgba(78,205,196,.15);color:var(--accent2)}
.done-box{text-align:center;padding:3rem 1rem}
.done-box .big{font-size:3rem}
.done-box h2{margin:.6rem 0}
.done-box p{color:var(--muted)}

/* test mode */
.quiz-q{background:var(--bg2);border:1px solid var(--line);border-radius:20px;padding:2rem;width:100%;max-width:560px;text-align:center;font-size:1.25rem;font-weight:600;margin-bottom:1.2rem}
.quiz-opts{display:flex;flex-direction:column;gap:.7rem;width:100%;max-width:560px}
.quiz-opt{background:var(--bg2);border:1px solid var(--line);border-radius:14px;padding:1rem 1.2rem;text-align:left;font-size:.98rem;transition:.15s}
.quiz-opt:hover{border-color:var(--accent)}
.quiz-opt.correct{border-color:var(--ok);background:rgba(94,211,158,.12)}
.quiz-opt.wrong{border-color:var(--danger);background:rgba(255,107,107,.12)}

/* match game */
.match-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:.7rem;width:100%;max-width:640px;margin-top:.6rem}
@media(max-width:560px){.match-grid{grid-template-columns:repeat(3,1fr)}}
.match-tile{aspect-ratio:1;background:var(--bg2);border:1px solid var(--line);border-radius:14px;display:flex;align-items:center;justify-content:center;padding:.5rem;font-size:.8rem;text-align:center;overflow:hidden;transition:.18s;overflow-wrap:anywhere}
.match-tile:hover{border-color:var(--accent)}
.match-tile.sel{border-color:var(--accent);background:rgba(124,108,255,.15);transform:scale(.96)}
.match-tile.matched{opacity:0;pointer-events:none;transform:scale(.7)}
.match-tile.shake{animation:shake .3s}
@keyframes shake{25%{transform:translateX(-5px)}75%{transform:translateX(5px)}}
.match-timer{font-size:1.3rem;font-weight:800;color:var(--accent2);margin:.5rem 0}

/* chart */
.chart{display:flex;align-items:flex-end;gap:4px;height:140px;background:var(--bg2);border:1px solid var(--line);border-radius:var(--radius);padding:1rem;margin-top:1rem}
.chart .bar{flex:1;background:var(--grad);border-radius:4px 4px 0 0;min-height:3px;position:relative}
.chart .bar span{position:absolute;bottom:-1.4rem;left:50%;transform:translateX(-50%);font-size:.6rem;color:var(--faint)}

/* modal */
.modal-bg{position:fixed;inset:0;background:rgba(0,0,0,.6);backdrop-filter:blur(4px);display:flex;align-items:flex-end;justify-content:center;z-index:50;animation:fadein .15s}
@media(min-width:600px){.modal-bg{align-items:center}}
@keyframes fadein{from{opacity:0}}
.modal{background:var(--bg2);border:1px solid var(--line);border-radius:20px 20px 0 0;padding:1.4rem;width:100%;max-width:520px;max-height:88dvh;overflow-y:auto;display:flex;flex-direction:column;gap:.9rem}
@media(min-width:600px){.modal{border-radius:20px}}
.modal h3{font-size:1.15rem}
.modal .row2{display:flex;gap:.6rem}
.modal .row2 .btn{flex:1}

/* bottom nav */
.bottomnav{position:fixed;bottom:0;left:0;right:0;background:rgba(23,26,35,.92);backdrop-filter:blur(12px);border-top:1px solid var(--line);display:flex;justify-content:space-around;padding:.5rem 0 calc(.5rem + var(--safe-b));z-index:20}
.bottomnav button{display:flex;flex-direction:column;align-items:center;gap:.15rem;font-size:.65rem;color:var(--faint);padding:.3rem 1rem;border-radius:10px}
.bottomnav button.active{color:var(--accent2)}
.bottomnav button .ic{font-size:1.25rem}

/* toast */
#toast{position:fixed;top:1rem;left:50%;transform:translateX(-50%);z-index:100;display:flex;flex-direction:column;gap:.5rem;width:min(92vw,420px)}
.toast-msg{background:var(--bg3);border:1px solid var(--line);border-left:3px solid var(--accent2);padding:.8rem 1rem;border-radius:12px;font-size:.9rem;box-shadow:var(--shadow);animation:slidein .25s}
.toast-msg.error{border-left-color:var(--danger)}
@keyframes slidein{from{transform:translateY(-10px);opacity:0}}

/* offline + folders */
#offlinebar{position:sticky;top:0;z-index:60;background:rgba(255,184,77,.14);color:var(--warn);border-bottom:1px solid rgba(255,184,77,.3);text-align:center;font-size:.83rem;padding:.5rem .8rem}
.folder-head{margin:1.4rem 0 -.4rem;font-weight:700;font-size:.95rem;color:var(--muted)}

/* kid-friendly touches */
.howto{background:var(--bg2);border:1px solid var(--line);border-radius:20px;padding:1.4rem;margin-top:1rem}
.howto h3{margin-bottom:1rem;font-size:1.1rem}
.howto-step{display:flex;align-items:flex-start;gap:.8rem;color:var(--muted);font-size:.95rem;margin-bottom:.9rem;line-height:1.45}
.howto-num{flex-shrink:0;width:26px;height:26px;border-radius:50%;background:var(--grad);color:#fff;font-weight:800;font-size:.85rem;display:flex;align-items:center;justify-content:center}
.confetti{position:fixed;top:-12px;width:10px;height:10px;border-radius:2px;z-index:200;pointer-events:none;animation:confetti-fall linear forwards}
@keyframes confetti-fall{to{transform:translateY(105vh) rotate(720deg);opacity:.7}}

/* images */
.row-img{max-width:120px;max-height:80px;border-radius:8px;margin:.3rem 0;display:block}
.study-img{max-width:100%;max-height:150px;border-radius:10px;margin-top:.7rem;display:block;margin-left:auto;margin-right:auto}

/* star */
.ops button.starred{color:var(--warn)}
.imgctl{margin:-.4rem 0 .6rem}
.imgpick{cursor:pointer}

/* TTS */
.ttsbtn{position:absolute;top:.8rem;right:1rem;font-size:1.1rem;opacity:.6;padding:.3rem;border-radius:8px;z-index:2}
.ttsbtn:hover{opacity:1;background:var(--bg3)}

/* activity heatmap */
.heatmap-wrap{background:var(--bg2);border:1px solid var(--line);border-radius:var(--radius);padding:1rem;overflow-x:auto;margin-top:.8rem}
.heatmap{display:grid;grid-template-rows:repeat(7,12px);grid-auto-flow:column;grid-auto-columns:12px;gap:3px;min-width:max-content}
.hm-cell{width:12px;height:12px;border-radius:3px;background:var(--bg3)}
.hm-1{background:#2d3f5e}.hm-2{background:#40598f}.hm-3{background:#7c6cff}.hm-4{background:#4ecdc4}

select.btn{appearance:none;text-align:left;font-size:.85rem;padding:.6rem .9rem}

.section-title{display:flex;align-items:center;justify-content:space-between;margin-top:1.6rem}
.section-title h2{font-size:1.1rem}
.spinner{width:22px;height:22px;border:3px solid var(--line);border-top-color:var(--accent);border-radius:50%;animation:spin .7s linear infinite;margin:0 auto}
@keyframes spin{to{transform:rotate(360deg)}}
.center{text-align:center;padding:2rem}