:root{
  --bg:#07111f;
  --panel:#0c192b;
  --panel2:#10213a;
  --line:#203652;
  --text:#eef7ff;
  --muted:#9fb3c8;
  --cyan:#6ee7ff;
  --violet:#9b87f5;
  --green:#6ee7b7;
  --amber:#ffd166;
  --danger:#ff7b8a;
  --shadow:0 18px 45px rgba(0,0,0,.25);
  --r:22px;
}
*{box-sizing:border-box}
html{background:var(--bg);scroll-behavior:smooth}
body{
  margin:0;
  background:
    radial-gradient(circle at 10% 0%,rgba(110,231,255,.10),transparent 25rem),
    radial-gradient(circle at 100% 20%,rgba(155,135,245,.09),transparent 28rem),
    var(--bg);
  color:var(--text);
  font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
  min-height:100vh
}
button,input,textarea{font:inherit}
button{cursor:pointer}
a{color:inherit;text-decoration:none}
.shell{max-width:980px;margin:auto;padding:18px 16px 100px}
.topbar{
  position:sticky;top:0;z-index:20;
  margin:-18px -16px 18px;
  padding:14px 16px;
  display:flex;align-items:center;justify-content:space-between;
  background:rgba(7,17,31,.88);backdrop-filter:blur(18px);
  border-bottom:1px solid rgba(255,255,255,.06)
}
.brand{display:flex;gap:11px;align-items:center;font-weight:850;letter-spacing:.2px}
.logo{width:38px;height:38px;border-radius:13px;background:linear-gradient(135deg,var(--cyan),var(--violet));color:#07111f;display:grid;place-items:center;font-weight:950}
.pill{font-size:12px;color:var(--muted);border:1px solid var(--line);padding:7px 10px;border-radius:999px;background:rgba(255,255,255,.025)}
.hero{
  border:1px solid var(--line);border-radius:28px;padding:25px;
  background:linear-gradient(145deg,rgba(16,33,58,.97),rgba(9,22,38,.96));
  box-shadow:var(--shadow);overflow:hidden;position:relative
}
.hero:after{content:"";position:absolute;width:180px;height:180px;border-radius:50%;background:rgba(110,231,255,.11);right:-70px;top:-70px;filter:blur(4px)}
.kicker{font-size:13px;color:var(--cyan);font-weight:800;text-transform:uppercase;letter-spacing:1.2px}
h1{font-size:clamp(30px,7vw,52px);line-height:1.02;margin:10px 0 13px;max-width:760px}
h2{font-size:24px;margin:0 0 14px}
h3{font-size:18px;margin:0 0 10px}
p{line-height:1.65;color:#d7e3ee}
.muted{color:var(--muted)}
.hero-actions,.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.btn{
  border:0;border-radius:14px;padding:13px 16px;font-weight:800;
  background:linear-gradient(135deg,var(--cyan),#87b8ff);color:#06101b
}
.btn.secondary{background:transparent;color:var(--text);border:1px solid var(--line)}
.btn.small{padding:9px 12px;font-size:13px}
.grid{display:grid;gap:14px;margin-top:16px}
.grid.two{grid-template-columns:repeat(2,minmax(0,1fr))}
.card{
  border:1px solid var(--line);background:rgba(12,25,43,.88);
  border-radius:var(--r);padding:18px;box-shadow:0 10px 35px rgba(0,0,0,.12)
}
.course-card{display:flex;gap:14px;align-items:flex-start}
.course-icon{width:46px;height:46px;border-radius:15px;display:grid;place-items:center;background:var(--panel2);font-size:22px;flex:0 0 auto}
.locked{opacity:.65}
.progress-wrap{margin-top:18px}
.progress-line{height:10px;border-radius:99px;background:#14243a;overflow:hidden}
.progress-bar{height:100%;width:0;background:linear-gradient(90deg,var(--cyan),var(--violet));transition:width .35s}
.progress-meta{display:flex;justify-content:space-between;color:var(--muted);font-size:13px;margin-top:8px}
.section-title{margin:30px 0 10px}
.lesson-list{display:grid;gap:10px}
.lesson{
  display:flex;align-items:center;gap:13px;padding:14px;border:1px solid var(--line);
  border-radius:16px;background:rgba(255,255,255,.018)
}
.lesson-num{width:36px;height:36px;border-radius:12px;display:grid;place-items:center;background:#122641;color:var(--cyan);font-weight:900}
.lesson-main{flex:1}.lesson-main strong{display:block}.lesson-main span{font-size:13px;color:var(--muted)}
.tag{font-size:11px;font-weight:850;padding:5px 8px;border-radius:999px;background:rgba(110,231,183,.11);color:var(--green);border:1px solid rgba(110,231,183,.2)}
.bottom-nav{
  position:fixed;z-index:30;left:50%;transform:translateX(-50%);bottom:10px;
  width:min(92%,620px);display:grid;grid-template-columns:repeat(4,1fr);gap:5px;
  background:rgba(9,20,35,.94);backdrop-filter:blur(20px);border:1px solid var(--line);
  border-radius:20px;padding:8px;box-shadow:var(--shadow)
}
.navbtn{border:0;background:transparent;color:var(--muted);padding:9px 5px;border-radius:12px;font-size:11px}
.navbtn b{display:block;font-size:18px;margin-bottom:2px}.navbtn.active{background:#10223a;color:var(--text)}
.lesson-head{margin-bottom:18px}
.breadcrumb{font-size:13px;color:var(--muted);margin-bottom:12px}
.mode-switch{display:grid;grid-template-columns:repeat(3,1fr);gap:6px;background:#091728;border:1px solid var(--line);border-radius:14px;padding:5px;margin:16px 0}
.mode-switch button{border:0;background:transparent;color:var(--muted);padding:10px 6px;border-radius:10px;font-size:12px;font-weight:800}
.mode-switch button.active{background:#17304f;color:var(--text)}
.block{margin:14px 0;border:1px solid var(--line);border-radius:20px;padding:18px;background:rgba(12,25,43,.8)}
.block .eyebrow{font-size:12px;font-weight:900;letter-spacing:.7px;text-transform:uppercase;color:var(--cyan);margin-bottom:9px}
.block.attack{border-color:rgba(255,123,138,.35);background:rgba(80,20,32,.18)}
.block.attack .eyebrow{color:var(--danger)}
.block.task{border-color:rgba(255,209,102,.32)}.block.task .eyebrow{color:var(--amber)}
.diagram{
  margin:14px 0;padding:18px;border-radius:18px;background:#06101c;border:1px solid #18314d;
  font-family:ui-monospace,SFMono-Regular,Menlo,monospace;white-space:pre-wrap;line-height:1.7;color:#d7f7ff;overflow:auto
}
.bits{display:grid;grid-template-columns:repeat(8,1fr);gap:7px;margin:16px 0}
.bit{
  min-height:52px;border:1px solid #31506f;background:#0a1728;color:var(--text);
  border-radius:12px;font-weight:950;font-size:18px
}
.bit.on{background:linear-gradient(135deg,#174663,#352b6a);border-color:var(--cyan);color:#fff}
.lab-output{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}
.stat{background:#081524;border:1px solid var(--line);border-radius:14px;padding:12px;min-width:0}
.stat small{display:block;color:var(--muted);font-size:11px}.stat strong{display:block;margin-top:5px;word-break:break-all}
.codepoints{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.codepoint{background:#071321;border:1px solid var(--line);border-radius:14px;padding:14px;text-align:center}
.codepoint .char{font-size:40px;font-weight:900}.codepoint code{font-size:12px;color:var(--cyan)}
.quiz-q{margin:18px 0}.answers{display:grid;gap:8px;margin-top:9px}
.answer{border:1px solid var(--line);background:#091828;color:var(--text);text-align:left;padding:12px;border-radius:12px}
.answer.correct{border-color:var(--green);background:rgba(110,231,183,.09)}
.answer.wrong{border-color:var(--danger);background:rgba(255,123,138,.08)}
textarea{
  width:100%;min-height:150px;background:#06111e;border:1px solid var(--line);
  border-radius:14px;color:var(--text);padding:14px;resize:vertical;outline:none
}
textarea:focus{border-color:var(--cyan)}
.toast{position:fixed;right:16px;top:78px;z-index:50;background:#10263d;border:1px solid var(--line);padding:12px 14px;border-radius:14px;box-shadow:var(--shadow)}
.hidden{display:none!important}
.footer-note{font-size:12px;color:var(--muted);text-align:center;margin:28px auto;max-width:680px}
@media(max-width:700px){
  .grid.two{grid-template-columns:1fr}
  .hero{padding:20px}
  .lab-output{grid-template-columns:1fr}
  .bits{gap:5px}.bit{min-height:48px;padding:0}
  .codepoints{grid-template-columns:1fr}
}


/* Phase 01.1 — mobile polish and pedagogy */
.shell{
  padding-bottom:calc(150px + env(safe-area-inset-bottom));
}
.bottom-nav{
  bottom:calc(10px + env(safe-area-inset-bottom));
}
.lesson{
  width:100%;
  color:var(--text);
  text-align:left;
  appearance:none;
  -webkit-appearance:none;
}
.lesson-main strong{
  color:var(--text);
}
.lesson.locked .lesson-main strong{
  color:#b4c1cf;
}
.mode-hint{
  margin:-6px 4px 14px;
  font-size:12px;
  color:var(--muted);
}
.why{
  border-color:rgba(110,231,255,.30);
  background:linear-gradient(145deg,rgba(12,37,54,.72),rgba(12,25,43,.8));
}
.security-grid{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:9px;
  margin:16px 0;
}
.security-mini{
  display:flex;
  flex-direction:column;
  gap:7px;
  min-height:130px;
  padding:13px;
  border:1px solid var(--line);
  background:#071321;
  border-radius:14px;
}
.security-mini strong{font-size:13px}
.security-mini span{font-size:12px;line-height:1.55;color:#c8d5e2}
.security-mini.red{border-color:rgba(255,123,138,.34)}
.security-mini.blue{border-color:rgba(110,231,255,.32)}
.security-mini.violet{border-color:rgba(155,135,245,.36)}
.compare-grid{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:9px;
}
.compare-grid>div{
  background:#071321;
  border:1px solid var(--line);
  border-radius:14px;
  padding:14px;
}
.compare-grid strong{
  display:block;
  color:var(--cyan);
  margin-bottom:8px;
}
.compare-grid span{
  display:block;
  font-size:12px;
  line-height:1.6;
  color:#cbd8e4;
}
.summary-list{
  display:grid;
  gap:10px;
}
.summary-list>div{
  padding:12px 13px;
  background:#071321;
  border:1px solid var(--line);
  border-radius:13px;
  line-height:1.55;
}
.summary-list b{color:var(--cyan)}
@media(max-width:700px){
  .security-grid,.compare-grid{grid-template-columns:1fr}
  .security-mini{min-height:0}
  .bottom-nav{width:calc(100% - 28px)}
}

/* Phase 02 */
.field-label{
  display:block;
  color:var(--muted);
  font-size:12px;
  margin:7px 0 7px;
}
.lab-input{
  width:100%;
  border:1px solid var(--line);
  border-radius:14px;
  background:#06111e;
  color:var(--text);
  padding:14px;
  outline:none;
}
.lab-input:focus{border-color:var(--cyan)}
.mono, code{
  font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
.converter-arrow{
  text-align:center;
  color:var(--cyan);
  font-size:24px;
  padding:6px 0;
}
.lab-result{
  background:#071321;
  border:1px solid var(--line);
  border-radius:14px;
  padding:13px;
  min-width:0;
}
.lab-result small{
  display:block;
  color:var(--muted);
  font-size:11px;
  margin-bottom:5px;
}
.lab-result strong{
  display:block;
  word-break:break-all;
}
.byte-weights{
  display:grid;
  grid-template-columns:repeat(8,1fr);
  gap:5px;
  margin-top:12px;
}
.weight{
  border:1px solid var(--line);
  border-radius:11px;
  padding:8px 3px;
  text-align:center;
  background:#071321;
}
.weight span{
  display:block;
  color:var(--muted);
  font-size:9px;
}
.weight b{
  display:block;
  margin-top:4px;
}
.weight.on{
  border-color:var(--cyan);
  background:rgba(110,231,255,.08);
}
.triple-result{
  display:grid;
  grid-template-columns:repeat(3,1fr);
  gap:8px;
  margin-top:12px;
}
.inspector{
  display:grid;
  gap:8px;
  margin-top:12px;
}
.inspect-row{
  display:grid;
  grid-template-columns:58px 1fr 1fr;
  gap:9px;
  align-items:center;
  background:#071321;
  border:1px solid var(--line);
  border-radius:14px;
  padding:10px;
}
.inspect-char{
  font-size:30px;
  font-weight:900;
  text-align:center;
}
.inspect-row small{
  display:block;
  color:var(--muted);
  font-size:10px;
}
.inspect-row b{
  display:block;
  font-family:ui-monospace,SFMono-Regular,Menlo,monospace;
  font-size:12px;
  margin-top:4px;
  word-break:break-all;
}
.compact-area{
  width:100%;
  min-height:92px;
  background:#06111e;
  border:1px solid var(--line);
  border-radius:14px;
  color:var(--text);
  padding:13px;
  resize:vertical;
  outline:none;
}
.compact-area:focus{border-color:var(--cyan)}
.hash-result{
  margin-top:12px;
}
.hash-result strong{
  font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;
  line-height:1.7;
}
.compare-hashes{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:10px;
  margin-bottom:10px;
}
.compare-hashes code{
  display:block;
  margin-top:8px;
  padding:10px;
  border:1px solid var(--line);
  border-radius:12px;
  background:#06111e;
  color:#c9f5ff;
  font-size:10px;
  line-height:1.5;
  word-break:break-all;
}
.note-card h3{
  line-height:1.35;
}
.knowledge-map{
  display:flex;
  flex-direction:column;
  align-items:center;
  gap:8px;
  margin:16px 0 22px;
}
.map-node{
  width:min(100%,520px);
  border:1px solid var(--line);
  border-radius:15px;
  background:#081524;
  padding:13px;
  text-align:center;
  font-weight:800;
  color:#a9b8c8;
}
.map-node.done{
  color:#dffbf1;
  border-color:rgba(110,231,183,.40);
  background:rgba(110,231,183,.08);
}
.map-arrow{
  color:var(--cyan);
  font-size:19px;
}
.map-row{
  width:100%;
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:7px;
}
.map-row .map-node{
  font-size:12px;
}
@media(max-width:700px){
  .triple-result{grid-template-columns:1fr}
  .inspect-row{grid-template-columns:46px 1fr}
  .inspect-row>span:last-child{grid-column:2}
  .compare-hashes{grid-template-columns:1fr}
  .map-row{grid-template-columns:1fr 1fr}
  .byte-weights{gap:3px}
  .weight{padding:7px 1px}
  .weight span{font-size:8px}
}

/* Phase 02.2 — clickable learning branches */
.branch-card{
  width:100%;
  color:var(--text);
  text-align:left;
  appearance:none;
  -webkit-appearance:none;
  cursor:pointer;
  transition:transform .16s ease,border-color .16s ease,background .16s ease;
}
.branch-card:active{transform:scale(.985)}
.branch-card:hover{border-color:rgba(110,231,255,.42);background:rgba(16,33,58,.96)}
.branch-copy{flex:1;min-width:0}
.branch-open{display:inline-block;margin-top:12px;color:var(--cyan);font-size:12px;font-weight:850}
.branch-hero{display:grid;grid-template-columns:auto 1fr;gap:16px;align-items:start;margin-bottom:16px}
.branch-hero-icon{width:64px;height:64px;border-radius:20px;display:grid;place-items:center;background:#102641;border:1px solid var(--line);font-size:29px}
.branch-hero h1{margin-top:5px}
.branch-roadmap{display:grid;gap:9px}
.branch-roadmap>div{display:grid;grid-template-columns:42px 1fr;gap:10px;align-items:center;padding:12px;border:1px solid var(--line);border-radius:13px;background:#071321}
.branch-roadmap b{color:var(--cyan);font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
@media(max-width:600px){.branch-hero{grid-template-columns:1fr}.branch-hero-icon{width:54px;height:54px}}