:root{
  --ink:#1f3d3a;
  --ink-light:#2f5752;
  --paper:#f6f1e7;
  --paper-card:#fffdf8;
  --accent:#d9762b;
  --accent-soft:#fbe3cf;
  --good:#3a8a5a;
  --warn:#c9472b;
  --line:#e3dccd;
  --text:#27302f;
  --text-mute:#6f7a78;
  --font-display:'Noto Serif Bengali','Space Grotesk',serif;
  --font-body:'Noto Sans Bengali','Inter',sans-serif;
  --radius:14px;
}

*{box-sizing:border-box;}
html,body{margin:0;padding:0;}
body{
  font-family:var(--font-body);
  background:var(--paper);
  color:var(--text);
  min-height:100vh;
  padding-bottom:40px;
}

.hidden{display:none !important;}

/* Topbar */
.topbar{
  display:flex;
  justify-content:space-between;
  align-items:center;
  gap:12px;
  padding:18px 16px 10px;
  background:var(--ink);
  color:var(--paper);
  border-radius:0 0 20px 20px;
  flex-wrap:wrap;
}
.brand{display:flex;align-items:center;gap:10px;}
.brand-mark{
  font-family:var(--font-display);
  font-weight:700;
  font-size:1.8rem;
  background:var(--accent);
  color:var(--ink);
  width:46px;height:46px;
  display:flex;align-items:center;justify-content:center;
  border-radius:12px;
  flex-shrink:0;
}
.brand-text h1{
  font-family:var(--font-display);
  font-size:1.4rem;
  margin:0;
  letter-spacing:0.5px;
}
.brand-text p{
  margin:0;
  font-size:0.72rem;
  color:#b9d3cf;
  letter-spacing:0.5px;
}
.stats-pill{
  display:flex;
  gap:14px;
  background:rgba(255,255,255,0.08);
  border-radius:12px;
  padding:8px 14px;
}
.stat{display:flex;flex-direction:column;align-items:center;min-width:48px;}
.stat-num{font-family:var(--font-display);font-weight:700;font-size:1.15rem;}
.stat-label{font-size:0.62rem;color:#b9d3cf;letter-spacing:0.3px;}

/* Tabbar */
.tabbar{
  display:flex;
  overflow-x:auto;
  gap:6px;
  padding:14px 12px 6px;
  -webkit-overflow-scrolling:touch;
}
.tab{
  font-family:var(--font-body);
  font-weight:600;
  font-size:0.8rem;
  background:var(--paper-card);
  border:1px solid var(--line);
  border-radius:10px;
  padding:9px 12px;
  color:var(--text-mute);
  white-space:nowrap;
  cursor:pointer;
  display:flex;align-items:center;gap:6px;
  position:relative;
  transition:all .15s ease;
}
.tab .tab-num{
  font-family:var(--font-display);
  font-weight:700;
  font-size:0.7rem;
  color:var(--accent);
}
.tab.active{
  background:var(--ink);
  color:var(--paper);
  border-color:var(--ink);
}
.tab.active .tab-num{color:var(--accent);}
.badge{
  background:var(--accent);
  color:#fff;
  font-size:0.65rem;
  font-weight:700;
  border-radius:999px;
  padding:1px 6px;
  min-width:16px;
  text-align:center;
}
.badge:empty{display:none;}

/* Main / Screens */
#app{padding:6px 14px 20px;max-width:760px;margin:0 auto;}
.screen-head{margin:14px 0 12px;}
.screen-head h2{
  font-family:var(--font-display);
  font-size:1.25rem;
  margin:0 0 4px;
  color:var(--ink);
}
.screen-head .sub{
  margin:0;
  font-size:0.82rem;
  color:var(--text-mute);
}

/* Card list */
.card-list{display:flex;flex-direction:column;gap:10px;}

.rcard{
  background:var(--paper-card);
  border:1px solid var(--line);
  border-radius:var(--radius);
  padding:14px;
  cursor:pointer;
  transition:transform .12s ease, box-shadow .12s ease;
  position:relative;
}
.rcard:active{transform:scale(0.98);}
.rcard:hover{box-shadow:0 4px 14px rgba(31,61,58,0.08);}
.rcard-top{display:flex;justify-content:space-between;align-items:flex-start;gap:8px;}
.rcard h4{
  font-family:var(--font-display);
  font-size:1.02rem;
  margin:0;
  color:var(--ink);
  line-height:1.4;
}
.rcard-title-link{
  cursor:pointer;
}
.rcard-title-link:hover{
  text-decoration:underline;
}
.rcard p{
  margin:6px 0 0;
  font-size:0.83rem;
  color:var(--text-mute);
  line-height:1.5;
}
.tagrow{display:flex;gap:6px;flex-wrap:wrap;margin-top:8px;}
.tag{
  font-size:0.68rem;
  font-weight:600;
  padding:2px 8px;
  border-radius:999px;
  background:var(--accent-soft);
  color:var(--accent);
}
.tag.subj-Math{background:#dde6fb;color:#3756b0;}
.tag.subj-Physics{background:#e3ddfb;color:#5c3fb0;}
.tag.subj-Chemistry{background:#fbe0e6;color:#b03f6f;}
.tag.subj-Biology{background:#ddf3e2;color:#2f8350;}
.tag.subj-Vocabulary{background:#fff2d0;color:#a87a10;}
.tag.subj-General,.tag.subj-Other{background:#ececec;color:#666;}
.tag.due-overdue{background:#fbe0e0;color:var(--warn);}
.tag.due-today{background:#fff2d0;color:#a87a10;}
.tag.due-future{background:#e3f0ec;color:var(--good);}
.streakflag{
  font-size:0.7rem;
  font-weight:700;
  color:var(--accent);
  white-space:nowrap;
}
.rcard-img{
  width:100%;
  border-radius:10px;
  margin-top:8px;
  max-height:160px;
  object-fit:cover;
}

/* Today actions */
.due-actions{
  display:flex;gap:8px;margin-top:12px;
}
.due-actions button{
  flex:1;
  font-family:var(--font-body);
  font-weight:600;
  font-size:0.8rem;
  border:none;
  border-radius:10px;
  padding:9px 0;
  cursor:pointer;
  transition:opacity .12s;
}
.due-actions button:active{opacity:0.7;}
.btn-hard{background:#fbe0e0;color:var(--warn);}
.btn-good{background:#fff2d0;color:#a87a10;}
.btn-easy{background:#ddf3e2;color:var(--good);}

/* Empty state */
.empty-state{
  text-align:center;
  padding:40px 20px;
  color:var(--text-mute);
}
.empty-icon{
  font-size:2.4rem;
  color:var(--good);
  font-family:var(--font-display);
  margin-bottom:6px;
}
.empty-state h3{
  font-family:var(--font-display);
  color:var(--ink);
  margin:0 0 6px;
}
.empty-state p{margin:0;font-size:0.85rem;}

/* Forms */
.add-card{
  background:var(--paper-card);
  border:1px solid var(--line);
  border-radius:var(--radius);
  padding:14px;
  display:flex;flex-direction:column;gap:8px;
  margin-bottom:14px;
}
input[type=text],input[type=number],textarea,select{
  font-family:var(--font-body);
  font-size:0.9rem;
  padding:10px 12px;
  border:1px solid var(--line);
  border-radius:10px;
  background:#fff;
  color:var(--text);
  width:100%;
}
textarea{resize:vertical;}
.row{display:flex;gap:8px;}
.row select{flex:1;}
.row input[type=file]{flex:1;font-size:0.78rem;}
.img-preview{
  width:100%;max-height:160px;object-fit:cover;border-radius:10px;
}
.btn-primary{
  font-family:var(--font-body);
  font-weight:700;
  font-size:0.9rem;
  background:var(--accent);
  color:#fff;
  border:none;
  border-radius:10px;
  padding:11px 0;
  cursor:pointer;
}
.btn-primary:active{opacity:0.85;}
.btn-secondary{
  font-family:var(--font-body);
  font-weight:600;
  font-size:0.85rem;
  background:var(--paper-card);
  border:1px solid var(--line);
  color:var(--ink);
  border-radius:10px;
  padding:10px 14px;
  cursor:pointer;
  margin-bottom:12px;
}
.btn-danger{
  font-family:var(--font-body);
  font-weight:600;
  font-size:0.85rem;
  background:#fbe0e0;
  border:1px solid #f3c9c9;
  color:var(--warn);
  border-radius:10px;
  padding:10px 14px;
  cursor:pointer;
  margin-bottom:12px;
}

/* Search / filters */
.filter-row{margin-bottom:10px;}
.lib-filters{
  display:flex;gap:6px;overflow-x:auto;margin-bottom:10px;padding-bottom:2px;
  -webkit-overflow-scrolling:touch;
}
.chip{
  font-family:var(--font-body);
  font-size:0.78rem;font-weight:600;
  padding:7px 14px;border-radius:999px;
  border:1px solid var(--line);
  background:var(--paper-card);
  color:var(--text-mute);
  white-space:nowrap;
  cursor:pointer;
}
.chip.active{background:var(--ink);color:var(--paper);border-color:var(--ink);}

/* Progress */
.progress-grid{
  display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:18px;
}
.pcard{
  background:var(--paper-card);
  border:1px solid var(--line);
  border-radius:var(--radius);
  padding:16px;
  text-align:center;
}
.pnum{
  display:block;
  font-family:var(--font-display);
  font-size:1.7rem;font-weight:700;color:var(--ink);
}
.plabel{font-size:0.75rem;color:var(--text-mute);}

.heatmap-wrap h3,.xp-wrap h3,.danger-zone h3{
  font-family:var(--font-display);
  font-size:1rem;color:var(--ink);margin:0 0 8px;
}
.heatmap{
  display:grid;
  grid-template-columns:repeat(7,1fr);
  gap:5px;
  margin-bottom:20px;
}
.hcell{
  aspect-ratio:1;
  border-radius:4px;
  background:var(--line);
}
.hcell.l1{background:#cdeadd;}
.hcell.l2{background:#9bd6bb;}
.hcell.l3{background:#5fb98e;}
.hcell.l4{background:var(--good);}

.xp-wrap{margin-bottom:20px;}
.xp-bar{
  height:14px;background:var(--line);border-radius:999px;overflow:hidden;margin:6px 0;
}
.xp-fill{
  height:100%;background:linear-gradient(90deg,var(--accent),#f0a05c);
  border-radius:999px;transition:width .3s ease;
}

.danger-zone{
  display:flex;flex-direction:column;gap:0;
}

/* Modal */
.modal-backdrop{
  position:fixed;inset:0;background:rgba(31,61,58,0.45);
  display:flex;align-items:flex-end;justify-content:center;
  z-index:100;
}
.modal{
  background:var(--paper-card);
  border-radius:18px 18px 0 0;
  width:100%;max-width:760px;
  max-height:85vh;overflow-y:auto;
  padding:20px;
  animation:slideUp .2s ease;
}
@keyframes slideUp{from{transform:translateY(30px);opacity:0;}to{transform:translateY(0);opacity:1;}}
.modal h3{
  font-family:var(--font-display);
  margin:0 0 6px;color:var(--ink);font-size:1.2rem;
}
.modal .modal-sub{font-size:0.8rem;color:var(--text-mute);margin:0 0 14px;}
.modal-field{margin-bottom:10px;}
.modal-field label{
  display:block;font-size:0.72rem;font-weight:700;color:var(--text-mute);
  margin-bottom:4px;text-transform:uppercase;letter-spacing:0.5px;
}
.modal-field .val{font-size:0.92rem;line-height:1.6;}
.modal-img{width:100%;border-radius:10px;margin-bottom:10px;}
.modal-actions{display:flex;gap:8px;margin-top:14px;}
.modal-actions button{flex:1;}
.modal-close{
  position:absolute;top:14px;right:18px;
  background:none;border:none;font-size:1.4rem;color:var(--text-mute);cursor:pointer;
}

/* Toast */
.toast{
  position:fixed;bottom:18px;left:50%;transform:translateX(-50%) translateY(60px);
  background:var(--ink);color:var(--paper);
  padding:10px 20px;border-radius:999px;
  font-size:0.85rem;font-weight:600;
  z-index:200;
  opacity:0;
  transition:all .25s ease;
  pointer-events:none;
}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0);}

@media (min-width:520px){
  .progress-grid{grid-template-columns:repeat(4,1fr);}
}

/* ---------- AI Flashcards ---------- */
#apiKeyInput{font-family:'Inter',monospace;font-size:0.82rem;}

.flash-grid{
  display:grid;
  grid-template-columns:1fr;
  gap:16px;
}
@media (min-width:560px){
  .flash-grid{grid-template-columns:1fr 1fr;}
}

.flashcard{
  perspective:1200px;
  height:200px;
  cursor:pointer;
  margin-top:10px;
}
.flashcard-inner{
  position:relative;
  width:100%;height:100%;
  transition:transform .6s cubic-bezier(.4,.2,.2,1);
  transform-style:preserve-3d;
}
.flashcard.flipped .flashcard-inner{
  transform:rotateY(180deg);
}
.flashcard-face{
  position:absolute;inset:0;
  -webkit-backface-visibility:hidden;
  backface-visibility:hidden;
  border-radius:var(--radius);
  border:1px solid var(--line);
  padding:16px;
  display:flex;flex-direction:column;
  overflow-y:auto;
}
.flashcard-front{
  background:var(--paper-card);
  justify-content:center;
}
.flashcard-back{
  background:var(--ink);
  color:var(--paper);
  transform:rotateY(180deg);
}
.flashcard-front h4{
  font-family:var(--font-display);
  font-size:1.1rem;
  color:var(--ink);
  margin:0;
  text-align:center;
}
.flashcard-front .flip-hint{
  position:absolute;bottom:10px;right:14px;
  font-size:0.68rem;color:var(--text-mute);
}
.flashcard-back h5{
  font-family:var(--font-display);
  font-size:0.95rem;
  margin:0 0 6px;
  color:var(--accent-soft);
}
.flashcard-back p{
  font-size:0.83rem;line-height:1.55;margin:0 0 8px;
  white-space:pre-line;
}
.flashcard-back .tag{
  background:rgba(255,255,255,0.12);color:var(--paper);
  margin-bottom:6px;display:inline-block;
}
.spinner{
  display:inline-block;width:14px;height:14px;
  border:2px solid var(--line);border-top-color:var(--accent);
  border-radius:50%;
  animation:spin 0.7s linear infinite;
  vertical-align:middle;margin-right:6px;
}
@keyframes spin{to{transform:rotate(360deg);}}