:root{
  --bg:#0b0e17; --bg2:#111527; --card:#161b30; --card2:#1c2240;
  --line:#262d4d; --text:#e8eaf6; --muted:#8b93b8;
  --accent:#6366f1; --accent2:#22d3ee; --good:#34d399; --warn:#fbbf24; --bad:#f87171;
  --radius:14px;
}
*{box-sizing:border-box; margin:0; padding:0}
html{-webkit-text-size-adjust:100%}
body{background:var(--bg); color:var(--text); font-family:'Space Grotesk',system-ui,-apple-system,sans-serif; line-height:1.55; min-height:100vh}
a{color:var(--accent2); text-decoration:none}
.wrap{max-width:1080px; margin:0 auto; padding:0 16px}
.hidden{display:none !important}
.muted{color:var(--muted)}
.center{text-align:center}
h1,h2,h3{line-height:1.25}
input,select,textarea{
  width:100%; background:var(--bg2); border:1px solid var(--line); color:var(--text);
  border-radius:10px; padding:11px 13px; font:inherit; margin:4px 0 14px;
}
input:focus,select:focus,textarea:focus{outline:none; border-color:var(--accent)}
label{font-size:.85rem; font-weight:600; color:var(--muted)}
button{font:inherit; cursor:pointer; border:none; border-radius:10px}
.btn-primary{background:linear-gradient(135deg,var(--accent),#8b5cf6); color:#fff; font-weight:700; padding:12px 22px}
.btn-primary:disabled{opacity:.5; cursor:default}
.btn-ghost{background:transparent; border:1px solid var(--line); color:var(--text); padding:10px 16px}
.btn-ghost:hover{border-color:var(--accent)}
.btn-danger{background:transparent; border:1px solid var(--bad); color:var(--bad); padding:8px 14px}
.btn-block{width:100%}
.btn-sm{padding:6px 12px; font-size:.85rem}

/* landing */
.landing-hero{padding:46px 0 24px}
.landing-hero h1{font-size:clamp(2rem,6vw,3.2rem); font-weight:800}
.landing-hero .grad{background:linear-gradient(90deg,var(--accent2),#8b5cf6); -webkit-background-clip:text; background-clip:text; color:transparent}
.landing-hero .sub{color:var(--muted); max-width:600px; margin-top:12px; font-size:1.05rem}

/* topbar / nav */
.topbar{display:flex; align-items:center; justify-content:space-between; padding:14px 0; gap:12px}
.brand{display:flex; align-items:center; gap:10px}
.logo-mark{width:40px; height:40px; border-radius:12px; background:linear-gradient(135deg,var(--accent),var(--accent2));
  display:flex; align-items:center; justify-content:center; font-size:1.3rem; font-weight:800; color:#fff}
.brand .word{font-weight:800; font-size:1.15rem; letter-spacing:.5px}
.brand .tagline{font-size:.72rem; color:var(--muted); margin-top:-3px}
.nav{display:flex; gap:4px; flex-wrap:wrap; padding:6px 0 14px}
.nav a{padding:9px 15px; border-radius:10px; color:var(--muted); font-weight:600; font-size:.95rem}
.nav a.active{background:var(--card2); color:var(--text)}
.nav a:hover{color:var(--text)}

.card{background:var(--card); border:1px solid var(--line); border-radius:var(--radius); padding:20px; margin:14px 0}
.card h2{font-size:1.15rem; margin-bottom:12px}
.grid{display:grid; gap:14px}
.grid.cols2{grid-template-columns:repeat(auto-fill,minmax(280px,1fr))}
.grid.cols4{grid-template-columns:repeat(auto-fit,minmax(140px,1fr))}

.stat{background:var(--card); border:1px solid var(--line); border-radius:var(--radius); padding:16px; text-align:center}
.stat .n{font-size:1.9rem; font-weight:800; color:var(--accent2)}
.stat .l{font-size:.8rem; color:var(--muted)}

.chip{display:inline-block; background:var(--bg2); border:1px solid var(--line); color:var(--muted);
  border-radius:999px; padding:7px 15px; font-size:.88rem; font-weight:600}
.chip.active{background:var(--accent); border-color:var(--accent); color:#fff}
.tabs{display:flex; gap:8px; flex-wrap:wrap; margin-bottom:14px}
.tabs .chip{cursor:pointer}

.badge{display:inline-block; padding:3px 10px; border-radius:999px; font-size:.72rem; font-weight:700; text-transform:uppercase; letter-spacing:.5px}
.badge.uploaded,.badge.downloading{background:#3b2f6b; color:#c4b5fd}
.badge.transcribing{background:#173f5f; color:#7dd3fc}
.badge.analyzing{background:#4a3413; color:#fcd34d}
.badge.ready{background:#0f3d2e; color:#6ee7b7}
.badge.error{background:#4c1d24; color:#fca5a5}

.class-card{border-top:4px solid var(--accent); cursor:pointer; transition:transform .12s}
.class-card:hover{transform:translateY(-2px)}
.class-card .code{font-size:.78rem; color:var(--muted); text-transform:uppercase; letter-spacing:1px}
.class-card h3{margin:2px 0 8px}
.class-card .meta{font-size:.85rem; color:var(--muted)}

.entry{padding:12px 0; border-bottom:1px solid var(--line); display:flex; gap:12px; align-items:flex-start; justify-content:space-between; flex-wrap:wrap}
.entry:last-child{border-bottom:none}
.entry .t{font-weight:700}
.entry .s{font-size:.83rem; color:var(--muted)}
.clickable{cursor:pointer}
.clickable:hover .t{color:var(--accent2)}

/* progress bars */
.bar{background:var(--bg2); border-radius:999px; height:10px; overflow:hidden; margin:6px 0}
.bar>i{display:block; height:100%; background:linear-gradient(90deg,var(--accent),var(--accent2)); border-radius:999px; transition:width .3s}

/* upload */
.drop{border:2px dashed var(--line); border-radius:var(--radius); padding:34px 20px; text-align:center; cursor:pointer; transition:border-color .15s}
.drop:hover,.drop.over{border-color:var(--accent)}
.drop .big{font-size:2.2rem}

/* flashcards */
.fc-stage{perspective:1200px; max-width:560px; margin:0 auto}
.fc{position:relative; width:100%; min-height:260px; transform-style:preserve-3d; transition:transform .45s; cursor:pointer}
.fc.flip{transform:rotateY(180deg)}
.fc>div{position:absolute; inset:0; backface-visibility:hidden; -webkit-backface-visibility:hidden; background:var(--card2);
  border:1px solid var(--line); border-radius:var(--radius); padding:26px; display:flex; align-items:center; justify-content:center; text-align:center; font-size:1.1rem; overflow:auto}
.fc .back{transform:rotateY(180deg); background:#1a2035}
.fc-actions{display:flex; gap:10px; justify-content:center; margin-top:18px}
.fc-actions button{padding:12px 22px; font-weight:700}
.b-again{background:#4c1d24; color:#fca5a5}
.b-good{background:#173f5f; color:#7dd3fc}
.b-easy{background:#0f3d2e; color:#6ee7b7}

/* quiz */
.q{margin-bottom:20px; padding-bottom:18px; border-bottom:1px solid var(--line)}
.q .qq{font-weight:700; margin-bottom:10px}
.opt{display:block; background:var(--bg2); border:1px solid var(--line); border-radius:10px; padding:11px 14px; margin:7px 0; cursor:pointer}
.opt:hover{border-color:var(--accent)}
.opt.sel{border-color:var(--accent); background:var(--card2)}
.opt.right{border-color:var(--good); background:#0f3d2e33}
.opt.wrong{border-color:var(--bad); background:#4c1d2433}
.result-line{padding:8px 12px; border-radius:10px; margin-top:8px; font-size:.92rem}
.result-line.right{background:#0f3d2e55; color:#6ee7b7}
.result-line.wrong{background:#4c1d2455; color:#fca5a5}

/* chat / ask */
.chat{display:flex; flex-direction:column; gap:12px; margin-bottom:16px}
.msg{max-width:85%; padding:13px 16px; border-radius:14px; font-size:.97rem}
.msg.user{align-self:flex-end; background:var(--accent); color:#fff; border-bottom-right-radius:4px}
.msg.ai{align-self:flex-start; background:var(--card2); border:1px solid var(--line); border-bottom-left-radius:4px}
.msg .src{margin-top:8px; font-size:.75rem; color:var(--muted)}
.askbar{display:flex; gap:8px; position:sticky; bottom:0; background:var(--bg); padding:10px 0}
.askbar textarea{flex:1; margin:0; min-height:52px; resize:vertical}
.askbar button{padding:0 22px}

/* markdown */
.md h1,.md h2,.md h3{margin:14px 0 8px}
.md p{margin:8px 0}
.md ul,.md ol{margin:8px 0 8px 22px}
.md li{margin:3px 0}
.md code{background:var(--bg2); padding:2px 6px; border-radius:6px; font-size:.9em}
.md pre{background:var(--bg2); padding:12px; border-radius:10px; overflow-x:auto; margin:10px 0}
.md strong{color:var(--accent2)}
.md blockquote{border-left:3px solid var(--accent); padding-left:12px; color:var(--muted); margin:8px 0}

/* outline */
.ol-h{font-weight:800; margin:14px 0 6px; color:var(--accent2)}
.ol-p{margin-left:14px; margin-top:6px; font-weight:600}
.ol-s{margin-left:34px; color:var(--muted); font-size:.93rem; margin-top:2px}

/* concept cards */
.concept{background:var(--card2); border:1px solid var(--line); border-radius:12px; padding:14px 16px; margin:10px 0}
.concept .c-name{font-weight:800; color:var(--accent2)}
.concept .c-why{font-size:.85rem; color:var(--muted); margin-top:6px; border-top:1px dashed var(--line); padding-top:6px}
.def{padding:8px 0; border-bottom:1px dashed var(--line)}
.def b{color:var(--accent2)}

/* tables */
table{width:100%; border-collapse:collapse; font-size:.9rem}
th{color:var(--muted); text-align:left; font-size:.75rem; text-transform:uppercase; letter-spacing:.6px; padding:8px}
td{padding:9px 8px; border-top:1px solid var(--line)}

/* modal */
.modal-bg{position:fixed; inset:0; background:#000a; display:flex; align-items:center; justify-content:center; z-index:50; padding:16px}
.modal{background:var(--card); border:1px solid var(--line); border-radius:var(--radius); padding:22px; width:100%; max-width:520px; max-height:92vh; overflow:auto}
.modal h2{margin-bottom:14px}
.form-row{display:grid; grid-template-columns:1fr 1fr; gap:0 14px}
@media (max-width:520px){.form-row{grid-template-columns:1fr}}

.toast{position:fixed; bottom:24px; left:50%; transform:translateX(-50%); background:var(--card2); border:1px solid var(--accent);
  border-radius:12px; padding:12px 22px; z-index:99; font-weight:600; max-width:90vw}
.spin{display:inline-block; width:16px; height:16px; border:2px solid var(--line); border-top-color:var(--accent2); border-radius:50%; animation:sp 0.8s linear infinite; vertical-align:-3px}
@keyframes sp{to{transform:rotate(360deg)}}
.feature-ico{font-size:1.2rem; margin-right:6px}