:root{
  --bg:#0e1117; --bg2:#151a23; --panel:#1a212c; --line:#252d3a;
  --fg:#e6edf3; --fg2:#9aa7b8; --fg3:#5f6c7e;
  --accent:#4c8dff; --accent2:#7aa7ff; --green:#3fb950; --green-dim:#1c3a24;
  --amber:#d29922; --red:#f85149; --purple:#a371f7;
  --r:12px; --shadow:0 8px 32px rgba(0,0,0,.45);
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{height:100%}
body{
  background:var(--bg); color:var(--fg); overflow:hidden;
  font:15px/1.65 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  -webkit-font-smoothing:antialiased;
}
button{font:inherit;color:inherit;background:none;border:none;cursor:pointer}
a{color:var(--accent2);text-decoration:none}
a:hover{text-decoration:underline}
::-webkit-scrollbar{width:10px;height:10px}
::-webkit-scrollbar-thumb{background:#2b3442;border-radius:6px}
::-webkit-scrollbar-thumb:hover{background:#3a465a}
::-webkit-scrollbar-track{background:transparent}

.screen{position:absolute;inset:0;display:none;flex-direction:column;overflow:hidden}
.screen.on{display:flex}

/* ---------- home ---------- */
#screen-home{align-items:center;justify-content:flex-start;overflow-y:auto;padding:0 24px}
.home-inner{width:100%;max-width:880px;margin:auto;padding:64px 0 48px}
.brand{text-align:center;margin-bottom:38px}
.brand h1{font-size:36px;font-weight:650;letter-spacing:-.5px}
.brand h1 span{color:var(--accent)}
.brand p{color:var(--fg2);margin-top:10px;font-size:15px}
.searchbox{position:relative;display:flex;gap:10px;align-items:flex-end;
  background:var(--panel);border:1px solid var(--line);border-radius:16px;
  padding:14px 14px 14px 18px;transition:border-color .18s,box-shadow .18s}
.searchbox:focus-within{border-color:var(--accent);box-shadow:0 0 0 4px rgba(76,141,255,.12)}
.searchbox textarea{flex:1;background:none;border:none;outline:none;color:var(--fg);
  font:inherit;resize:none;min-height:26px;max-height:150px;line-height:1.6}
.searchbox textarea::placeholder{color:var(--fg3)}
.btn-go{background:var(--accent);color:#fff;border-radius:10px;padding:9px 20px;
  font-weight:600;font-size:14px;white-space:nowrap;transition:background .15s,transform .1s}
.btn-go:hover{background:#3b7ae8}
.btn-go:active{transform:scale(.97)}
.btn-go:disabled{background:#2b3442;color:var(--fg3);cursor:not-allowed}
.hints{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px;justify-content:center}
.hint{font-size:13px;color:var(--fg2);background:var(--bg2);border:1px solid var(--line);
  border-radius:999px;padding:5px 13px;transition:all .15s}
.hint:hover{color:var(--fg);border-color:var(--accent);background:#1c2431}

.history{margin-top:52px}
.history-head{display:flex;align-items:center;gap:10px;margin-bottom:16px;
  color:var(--fg2);font-size:13px;font-weight:600;letter-spacing:.3px}
.history-head:before,.history-head:after{content:"";flex:1;height:1px;background:var(--line)}
.history-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(212px,1fr));gap:14px}
.hcard{background:var(--panel);border:1px solid var(--line);border-radius:var(--r);
  overflow:hidden;cursor:pointer;transition:transform .16s,border-color .16s,box-shadow .16s}
.hcard:hover{transform:translateY(-3px);border-color:var(--accent);box-shadow:var(--shadow)}
.hcard .thumb{height:112px;background:radial-gradient(ellipse at 50% 40%,#1b2431,#12171f);
  border-bottom:1px solid var(--line);display:block;width:100%}
.hcard .meta{padding:11px 13px}
.hcard .k{font-weight:600;font-size:14px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.hcard .sub{color:var(--fg3);font-size:12px;margin-top:4px;display:flex;gap:8px;flex-wrap:wrap}
.hcard .sub .done{color:var(--green)}
.empty{color:var(--fg3);text-align:center;padding:26px;font-size:14px;
  border:1px dashed var(--line);border-radius:var(--r)}

/* ---------- top bar ---------- */
.topbar{display:flex;align-items:center;gap:14px;padding:12px 20px;
  border-bottom:1px solid var(--line);background:var(--bg2);flex-shrink:0;z-index:5}
.topbar .title{font-weight:600;font-size:15px;flex-shrink:0}
.topbar .crumb{color:var(--fg3);font-size:13px;overflow:hidden;text-overflow:ellipsis;
  white-space:nowrap;flex:1}
.btn-ghost{border:1px solid var(--line);border-radius:8px;padding:6px 13px;
  font-size:13px;color:var(--fg2);transition:all .15s;white-space:nowrap}
.btn-ghost:hover{color:var(--fg);border-color:var(--accent);background:#1c2431}

/* ---------- graph ---------- */
#graph-wrap{flex:1;position:relative;overflow:hidden;
  background:radial-gradient(ellipse at 50% 35%,#141b26 0%,var(--bg) 70%)}
#graph-svg{width:100%;height:100%;display:block;cursor:grab}
#graph-svg.dragging{cursor:grabbing}
.gnode{cursor:pointer}
.gnode circle{transition:stroke .18s,filter .18s,fill .18s}
.gnode:hover circle{filter:brightness(1.35)}
.gnode text{pointer-events:none;user-select:none;text-anchor:middle;
  font-weight:500;paint-order:stroke;stroke:var(--bg);stroke-width:3.5px;stroke-linejoin:round}
.gnode .badge{font-size:10px;font-weight:700;fill:var(--bg);stroke:none}
.glink{fill:none;stroke:#42526b;stroke-opacity:.6;stroke-width:1.7}
.glink.hot{stroke:var(--accent);stroke-width:2.4;stroke-opacity:.75}
.legend{position:absolute;left:16px;bottom:16px;background:#151a23e0;backdrop-filter:blur(8px);
  border:1px solid var(--line);border-radius:10px;padding:11px 14px;font-size:12px;
  color:var(--fg2);line-height:1.9;pointer-events:none;max-width:250px}
.legend b{color:var(--fg);font-weight:600}
.legend .dot{display:inline-block;width:9px;height:9px;border-radius:50%;margin-right:6px;
  vertical-align:middle}

/* node inspector */
#inspector{position:absolute;right:18px;top:18px;width:308px;background:var(--panel);
  border:1px solid var(--line);border-radius:14px;box-shadow:var(--shadow);
  padding:17px;display:none;animation:pop .18s ease-out}
#inspector.on{display:block}
@keyframes pop{from{opacity:0;transform:translateY(-8px) scale(.97)}to{opacity:1;transform:none}}
#inspector .kind{font-size:11px;color:var(--fg3);letter-spacing:.6px;text-transform:uppercase;
  font-weight:700;margin-bottom:6px}
#inspector h3{font-size:18px;font-weight:650;line-height:1.35}
#inspector .desc{color:var(--fg2);font-size:13.5px;margin-top:9px}
#inspector .acts{display:flex;flex-direction:column;gap:8px;margin-top:15px}
.btn-learn{background:linear-gradient(135deg,var(--green),#2ea043);color:#fff;
  border-radius:10px;padding:11px;font-weight:650;font-size:14.5px;
  transition:filter .15s,transform .1s}
.btn-learn:hover{filter:brightness(1.12)}
.btn-learn:active{transform:scale(.98)}
.btn-learn.review{background:linear-gradient(135deg,#2f6f3f,#255c33)}
.tag-done{display:inline-flex;align-items:center;gap:5px;background:var(--green-dim);
  color:var(--green);border-radius:6px;padding:3px 9px;font-size:12px;
  font-weight:600;margin-top:10px}

/* ---------- waiting ---------- */
#screen-wait{align-items:center;justify-content:center;text-align:center;padding:30px}
.orbit{width:88px;height:88px;position:relative;margin-bottom:28px}
.orbit i{position:absolute;inset:0;border:2.5px solid transparent;border-radius:50%;
  border-top-color:var(--accent);animation:spin 1.15s linear infinite}
.orbit i:nth-child(2){inset:13px;border-top-color:var(--purple);animation-duration:1.7s;
  animation-direction:reverse}
.orbit i:nth-child(3){inset:26px;border-top-color:var(--green);animation-duration:2.3s}
@keyframes spin{to{transform:rotate(360deg)}}
#wait-title{font-size:20px;font-weight:600}
#wait-sub{color:var(--fg2);margin-top:9px;font-size:14px}
#wait-steps{margin-top:26px;text-align:left;width:min(520px,92vw);background:var(--panel);
  border:1px solid var(--line);border-radius:12px;padding:15px 18px;font-size:13.5px;
  color:var(--fg2);max-height:210px;overflow-y:auto}
#wait-steps div{padding:4px 0;display:flex;gap:9px;animation:fadein .3s}
#wait-steps div:last-child{color:var(--fg)}
#wait-steps .tick{color:var(--green);flex-shrink:0}
@keyframes fadein{from{opacity:0;transform:translateX(-6px)}to{opacity:1;transform:none}}
#wait-elapsed{color:var(--fg3);font-size:12.5px;margin-top:15px}
.wait-err{background:#2a1618;border:1px solid #5c2b2e;color:#ffb3b3;border-radius:12px;
  padding:15px 18px;margin-top:20px;width:min(520px,92vw);text-align:left;font-size:14px}

/* ---------- learn ---------- */
#learn-scroll{flex:1;overflow-y:auto;scroll-behavior:smooth}
.learn-inner{max-width:790px;margin:0 auto;padding:30px 22px 130px}
.learn-head h2{font-size:27px;font-weight:650;letter-spacing:-.3px}
.learn-head .path{color:var(--fg3);font-size:13px;margin-top:7px}
.learn-head .intro{color:var(--fg2);margin-top:13px;font-size:14.5px;
  border-left:3px solid var(--accent);padding-left:13px}
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--r);
  margin-top:19px;overflow:hidden;transition:border-color .2s,box-shadow .2s}
.card.learned{border-color:#2c5c39}
.card.flash{animation:flash 1.1s ease-out}
@keyframes flash{0%,100%{box-shadow:none}25%{box-shadow:0 0 0 3px rgba(210,153,34,.5)}}
.card-top{display:flex;align-items:center;gap:11px;padding:14px 18px;
  border-bottom:1px solid var(--line);background:#1d2530}
.card-n{width:25px;height:25px;border-radius:50%;background:#2b3442;color:var(--fg2);
  font-size:12px;font-weight:700;display:grid;place-items:center;flex-shrink:0}
.card.learned .card-n{background:var(--green);color:#0d1117}
.card-type{font-size:11px;font-weight:700;letter-spacing:.5px;padding:3px 8px;
  border-radius:5px;flex-shrink:0}
.t-text{background:#1d3a5c;color:#79b8ff}
.t-video{background:#4a1f2b;color:#ff9aae}
.t-link{background:#3a2d52;color:#c4a7ff}
.card-title{font-weight:600;font-size:15.5px;flex:1;min-width:0}
.card-body{padding:17px 19px;font-size:14.5px;color:#d3dbe4;overflow-wrap:break-word}
.card-body p{margin:.65em 0}
.card-body h1,.card-body h2,.card-body h3{font-size:16px;font-weight:650;margin:1.1em 0 .5em;color:var(--fg)}
.card-body ul,.card-body ol{margin:.65em 0 .65em 1.4em}
.card-body li{margin:.28em 0}
.card-body code{background:#0d1117;border:1px solid var(--line);border-radius:5px;
  padding:1.5px 5px;font-size:13px;font-family:"JetBrains Mono",Consolas,monospace;color:#ffa657}
.card-body pre{background:#0d1117;border:1px solid var(--line);border-radius:9px;
  padding:13px 15px;overflow-x:auto;margin:.85em 0}
.card-body pre code{background:none;border:none;padding:0;color:#c9d1d9;font-size:13px;line-height:1.6}
.card-body strong{color:#fff;font-weight:640}
.card-body blockquote{border-left:3px solid var(--line);padding-left:13px;color:var(--fg2);margin:.7em 0}
.res{display:flex;gap:13px;align-items:center;margin:0 19px 15px;padding:13px 15px;
  background:#0d1117;border:1px solid var(--line);border-radius:10px;transition:border-color .15s}
.res:hover{border-color:var(--accent)}
.res .ico{font-size:23px;flex-shrink:0}
.res .info{flex:1;min-width:0}
.res .info b{display:block;font-size:14px;font-weight:600;white-space:nowrap;
  overflow:hidden;text-overflow:ellipsis}
.res .info span{color:var(--fg3);font-size:12px;word-break:break-all}
.res .open{background:var(--accent);color:#fff;border-radius:7px;padding:7px 14px;
  font-size:13px;font-weight:600;flex-shrink:0}
.res .open:hover{background:#3b7ae8;text-decoration:none}
.kp{margin:0 19px 16px;padding:12px 15px;background:#161d27;border:1px solid var(--line);
  border-left:3px solid var(--amber);border-radius:0 9px 9px 0}
.kp b{font-size:12px;color:var(--amber);letter-spacing:.4px}
.kp ul{margin:7px 0 0 1.15em;font-size:13.5px;color:var(--fg2)}
.kp li{margin:3px 0}
.card-foot{display:flex;align-items:center;justify-content:flex-end;
  padding:12px 19px;border-top:1px solid var(--line);background:#161d27}
.chk{display:flex;align-items:center;gap:9px;cursor:pointer;user-select:none;
  font-size:14px;color:var(--fg2);transition:color .15s}
.chk:hover{color:var(--fg)}
.chk .box{width:21px;height:21px;border:2px solid #3d4a5c;border-radius:6px;
  display:grid;place-items:center;transition:all .18s}
.chk .box svg{width:12px;height:12px;stroke:#fff;stroke-width:3.4;fill:none;
  stroke-linecap:round;stroke-linejoin:round;opacity:0;transform:scale(.4);
  transition:all .18s}
.chk input{display:none}
.chk input:checked+.box{background:var(--green);border-color:var(--green)}
.chk input:checked+.box svg{opacity:1;transform:none}
.chk input:checked~span{color:var(--green);font-weight:600}

.learn-bar{position:absolute;left:0;right:0;bottom:0;background:#151a23f2;
  backdrop-filter:blur(12px);border-top:1px solid var(--line);padding:14px 22px;
  display:flex;align-items:center;gap:16px;justify-content:center}
.learn-bar .prog{flex:1;max-width:330px}
.learn-bar .prog .bar{height:6px;background:#252d3a;border-radius:99px;overflow:hidden}
.learn-bar .prog .bar i{display:block;height:100%;background:var(--green);
  border-radius:99px;transition:width .35s cubic-bezier(.4,0,.2,1);width:0}
.learn-bar .prog .txt{font-size:12.5px;color:var(--fg2);margin-top:6px}
.btn-test{background:var(--accent);color:#fff;border-radius:10px;padding:12px 30px;
  font-weight:650;font-size:15px;transition:all .16s;white-space:nowrap}
.btn-test:hover{background:#3b7ae8}
.btn-test.locked{background:#2b3442;color:var(--fg3)}
.btn-test.locked:hover{background:#333d4d}

.toast{position:fixed;left:50%;bottom:96px;transform:translate(-50%,20px);
  background:#2a2113;border:1px solid #5c4a1e;color:#ffd479;padding:12px 20px;
  border-radius:11px;font-size:14px;font-weight:500;box-shadow:var(--shadow);
  opacity:0;pointer-events:none;transition:all .28s cubic-bezier(.4,0,.2,1);z-index:99}
.toast.on{opacity:1;transform:translate(-50%,0)}

/* ---------- quiz ---------- */
#quiz-scroll{flex:1;overflow-y:auto}
.quiz-inner{max-width:790px;margin:0 auto;padding:30px 22px 60px}
.q{background:var(--panel);border:1px solid var(--line);border-radius:var(--r);
  padding:20px 22px;margin-top:17px}
.q-head{display:flex;gap:11px;align-items:baseline;margin-bottom:14px}
.q-n{font-size:12px;font-weight:700;color:var(--fg3);flex-shrink:0}
.q-multi{font-size:11px;background:#3a2d52;color:#c4a7ff;padding:2px 7px;
  border-radius:5px;font-weight:700;flex-shrink:0}
.q-stem{font-size:15.5px;font-weight:550;line-height:1.65;overflow-wrap:break-word}
.q-stem code{background:#0d1117;border-radius:4px;padding:1.5px 5px;font-size:13.5px;
  font-family:Consolas,monospace;color:#ffa657}
.opts{display:flex;flex-direction:column;gap:9px}
.opt{display:flex;gap:11px;align-items:flex-start;padding:12px 15px;border-radius:9px;
  border:1.5px solid var(--line);background:#161d27;cursor:pointer;transition:all .15s}
.opt:hover{border-color:#3d4a5c;background:#1a222d}
.opt.sel{border-color:var(--accent);background:#152238}
.opt .mark{width:20px;height:20px;flex-shrink:0;border:2px solid #3d4a5c;
  display:grid;place-items:center;font-size:11px;font-weight:700;color:transparent;
  transition:all .15s;margin-top:1px}
.opt.single .mark{border-radius:50%}
.opt.multi .mark{border-radius:5px}
.opt.sel .mark{border-color:var(--accent);background:var(--accent);color:#fff}
.opt .txt{flex:1;font-size:14.5px;line-height:1.55}
.opt.correct{border-color:var(--green);background:#132b1c}
.opt.correct .mark{border-color:var(--green);background:var(--green);color:#fff}
.opt.wrong{border-color:var(--red);background:#2c1618}
.opt.wrong .mark{border-color:var(--red);background:var(--red);color:#fff}
.q.graded .opt{cursor:default}
.q.graded .opt:hover{background:#161d27}
.q.graded .opt.correct:hover{background:#132b1c}
.q.graded .opt.wrong:hover{background:#2c1618}
.expl{margin-top:15px;padding:14px 16px;border-radius:10px;font-size:14px;
  line-height:1.7;animation:fadein .3s}
.expl.ok{background:#132b1c;border:1px solid #2c5c39;color:#a5d6b0}
.expl.no{background:#2a1618;border:1px solid #5c2b2e;color:#ffc2c2}
.expl b{display:block;margin-bottom:6px;font-size:13px;letter-spacing:.4px}
.score{background:var(--panel);border:1px solid var(--line);border-radius:16px;
  padding:28px;text-align:center;margin-top:22px}
.score .n{font-size:52px;font-weight:700;letter-spacing:-2px;line-height:1.1}
.score .n small{font-size:22px;color:var(--fg3);font-weight:500}
.score .lbl{color:var(--fg2);margin-top:8px;font-size:14.5px}
.score .wrongs{color:var(--fg3);font-size:13px;margin-top:6px}
.quiz-bar{display:flex;gap:12px;justify-content:center;margin-top:26px;flex-wrap:wrap}
.btn-submit{background:var(--accent);color:#fff;border-radius:10px;padding:13px 40px;
  font-weight:650;font-size:15px;transition:all .16s}
.btn-submit:hover{background:#3b7ae8}
.btn-submit:disabled{background:#2b3442;color:var(--fg3);cursor:not-allowed}
.btn-finish{background:linear-gradient(135deg,var(--green),#2ea043);color:#fff;
  border-radius:10px;padding:13px 40px;font-weight:650;font-size:15px}
.btn-finish:hover{filter:brightness(1.12)}