@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&family=IBM+Plex+Sans:wght@400;500;600&family=IBM+Plex+Mono:wght@400;500&display=swap');

:root{
  --ink:#0F1A24;
  --ink-2:#16232F;
  --paper:#EDEAE0;
  --paper-dim:#B9C2C9;
  --teal:#4FD1C5;
  --amber:#E8A94C;
  --slate:#5B6B7A;
  --line: rgba(237,234,224,0.12);
}
*{box-sizing:border-box;}
html,body{margin:0;padding:0;}
body{
  background:var(--ink);
  font-family:'IBM Plex Sans', sans-serif;
  color:var(--paper);
  line-height:1.5;
}
a{color:inherit; text-decoration:none;}
img{max-width:100%; display:block;}

/* ===== nav ===== */
.site-nav{
  display:flex; align-items:center; justify-content:space-between;
  padding:22px 48px; border-bottom:1px solid var(--line);
  position:sticky; top:0; background:var(--ink); z-index:10;
}
.brand{
  font-family:'Space Grotesk',sans-serif; font-weight:700; font-size:18px; color:var(--paper);
  display:flex; align-items:center; gap:8px;
}
.brand img{width:34px; height:34px; display:block;}
.brand .node{width:8px;height:8px;border-radius:50%;background:var(--teal);box-shadow:0 0 8px var(--teal);}
.nav-links{ display:flex; gap:32px; font-family:'IBM Plex Mono',monospace; font-size:12.5px; color:var(--paper-dim); }
.nav-links a:hover{color:var(--paper);}
.nav-links a.current{color:var(--teal);}
.nav-toggle{display:none;}

@media (max-width: 760px){
  .nav-links{
    display:none; position:absolute; top:100%; left:0; right:0; background:var(--ink);
    flex-direction:column; gap:0; border-bottom:1px solid var(--line);
  }
  .nav-links.open{display:flex;}
  .nav-links a{padding:14px 24px; border-top:1px solid var(--line);}
  .nav-toggle{
    display:block; background:none; border:1px solid var(--line); color:var(--paper);
    font-family:'IBM Plex Mono',monospace; border-radius:6px; padding:8px 12px; cursor:pointer;
  }
}

.eyebrow{
  font-family:'IBM Plex Mono',monospace; color:var(--amber); font-size:12.5px; letter-spacing:0.08em;
  display:flex; align-items:center; gap:8px; margin-bottom:18px;
}
.eyebrow::before{content:"$"; color:var(--teal);}

/* ===== hero (home) ===== */
.hero{
  padding:80px 48px 60px;
  display:grid; grid-template-columns:1.2fr 0.8fr; gap:40px; align-items:center;
  border-bottom:1px solid var(--line);
}
.hero h1{
  font-family:'Space Grotesk',sans-serif; font-size:46px; line-height:1.15; margin:0 0 18px; font-weight:700;
}
.hero h1 .accent{color:var(--teal);}
.hero p{ color:var(--paper-dim); font-size:16px; line-height:1.7; max-width:480px; margin:0 0 28px;}
.btn-row{display:flex; gap:14px; flex-wrap:wrap;}
.btn{
  font-family:'IBM Plex Mono',monospace; font-size:13px; padding:12px 22px; border-radius:6px;
  display:inline-block; border:1px solid var(--line);
}
.btn.primary{ background:var(--teal); color:#06201D; font-weight:600; border-color:var(--teal);}
.btn.ghost{ color:var(--paper);}
.btn:hover{ opacity:0.85; }

.terminal{
  background:var(--ink-2); border:1px solid var(--line); border-radius:10px; padding:20px 22px;
  font-family:'IBM Plex Mono',monospace; font-size:13px; color:var(--paper-dim); line-height:1.9;
}
.terminal .prompt{color:var(--teal);}
.terminal .out{color:var(--amber);}

@media (max-width: 760px){
  .hero{grid-template-columns:1fr; padding:48px 24px;}
  .hero h1{font-size:32px;}
}

.stats-row{ display:flex; padding:0 48px; border-bottom:1px solid var(--line); flex-wrap:wrap;}
.stat{ flex:1; min-width:160px; padding:26px 0; text-align:left; border-right:1px solid var(--line);}
.stat:last-child{border-right:none;}
.stat .num{font-family:'Space Grotesk',sans-serif; font-size:26px; color:var(--teal); font-weight:700;}
.stat .lbl{font-family:'IBM Plex Mono',monospace; font-size:11.5px; color:var(--slate); margin-top:4px;}

.section-head{ padding:44px 48px 10px; }
.section-head h2{font-family:'Space Grotesk',sans-serif; font-size:26px; margin:0; font-weight:600;}

.card-grid{ display:grid; grid-template-columns:repeat(3,1fr); gap:18px; padding:20px 48px 56px;}
@media (max-width:900px){ .card-grid{grid-template-columns:1fr;} }
.card{ background:var(--ink-2); border:1px solid var(--line); border-radius:10px; padding:22px;}
.card .tag{font-family:'IBM Plex Mono',monospace; font-size:10.5px; color:var(--amber); letter-spacing:0.05em;}
.card h3{font-family:'Space Grotesk',sans-serif; font-size:17px; margin:10px 0 8px;}
.card p{color:var(--paper-dim); font-size:13.5px; line-height:1.6; margin:0 0 14px;}
.stack{display:flex; gap:6px; flex-wrap:wrap;}
.chip{font-family:'IBM Plex Mono',monospace; font-size:10.5px; color:var(--teal); border:1px solid rgba(79,209,197,0.3); padding:3px 8px; border-radius:20px;}
.card-link{font-family:'IBM Plex Mono',monospace; font-size:12px; color:var(--amber); display:inline-block;}
.card-link:hover{color:var(--teal);}

/* ===== about ===== */
.about-wrap{ padding:56px 48px; display:grid; grid-template-columns:0.9fr 1.6fr; gap:48px;}
@media (max-width:800px){ .about-wrap{grid-template-columns:1fr; padding:40px 24px;} }
.avatar-block{ background:var(--ink-2); border:1px solid var(--line); border-radius:12px; padding:26px; height:fit-content;}
.avatar-ph{
  width:100%; aspect-ratio:1; border-radius:10px; background:linear-gradient(135deg,#1B2A35,#0F1A24);
  border:1px dashed var(--slate); display:flex; align-items:center; justify-content:center;
  color:var(--slate); font-family:'IBM Plex Mono',monospace; font-size:11px; margin-bottom:18px; overflow:hidden;
}
.avatar-ph img{width:100%; height:100%; object-fit:cover;}
.avatar-block h3{font-family:'Space Grotesk',sans-serif; margin:0 0 4px; font-size:19px;}
.avatar-block .role{color:var(--teal); font-family:'IBM Plex Mono',monospace; font-size:12px; margin-bottom:16px;}
.meta-line{display:flex; justify-content:space-between; font-size:12.5px; color:var(--paper-dim); padding:8px 0; border-top:1px solid var(--line); gap:12px;}
.meta-line b{color:var(--paper); font-weight:500; text-align:right;}
.about-copy h2{font-family:'Space Grotesk',sans-serif; font-size:28px; margin-top:0;}
.about-copy p{color:var(--paper-dim); line-height:1.8; font-size:15px;}
.subject-grid{display:grid; grid-template-columns:repeat(3,1fr); gap:14px; margin-top:24px;}
@media (max-width:600px){ .subject-grid{grid-template-columns:1fr;} }
.subject{ border:1px solid var(--line); border-radius:8px; padding:16px; font-family:'IBM Plex Mono',monospace;}
.subject .n{color:var(--amber); font-size:11px;}
.subject .t{color:var(--paper); font-size:13.5px; margin-top:6px;}

/* ===== projects ===== */
.proj-list{ padding:24px 48px 56px; display:flex; flex-direction:column; gap:16px;}
@media (max-width:700px){ .proj-list{padding:20px 20px 40px;} }
.proj-row{
  display:grid; grid-template-columns:60px 1fr auto; gap:24px; align-items:center;
  background:var(--ink-2); border:1px solid var(--line); border-radius:10px; padding:22px 26px;
}
@media (max-width:700px){ .proj-row{grid-template-columns:1fr; gap:10px;} }
.proj-idx{font-family:'IBM Plex Mono',monospace; color:var(--teal); font-size:22px; font-weight:600;}
.proj-row h3{font-family:'Space Grotesk',sans-serif; margin:0 0 6px; font-size:17px;}
.proj-row p{margin:0 0 10px; color:var(--paper-dim); font-size:13.5px; line-height:1.6;}
.proj-link{font-family:'IBM Plex Mono',monospace; font-size:12px; color:var(--amber);}
.proj-link:hover{color:var(--teal);}

/* ===== teaching : subject resource browser ===== */
:root{
  --violet:#B7A6F5; /* third subject accent, alongside --teal and --amber */
}

.section-intro{ padding:0 48px; margin:-6px 0 26px; color:var(--paper-dim); font-size:14.5px; line-height:1.65; max-width:60ch;}
@media (max-width:700px){ .section-intro{ padding:0 20px; } }

/* subject switcher */
.subject-tabs{ display:flex; gap:10px; flex-wrap:wrap; padding:0 48px; margin-bottom:20px;}
@media (max-width:700px){ .subject-tabs{ padding:0 20px; } }
.subj-tab{
  font-family:'IBM Plex Mono',monospace; font-size:12.5px; color:var(--paper-dim);
  background:var(--ink-2); border:1px solid var(--line); border-radius:8px;
  padding:10px 14px; display:flex; align-items:center; gap:8px; cursor:pointer;
  transition:border-color .2s ease, color .2s ease;
}
.subj-tab:hover{ color:var(--paper); }
.subj-tab .n{ font-size:10.5px; padding:2px 6px; border-radius:4px; background:rgba(237,234,224,0.06); color:var(--tab-accent, var(--slate)); }
.subj-tab[aria-pressed="true"]{ color:var(--paper); border-color:var(--tab-accent, var(--teal)); }
.subj-tab[aria-pressed="true"] .n{ background:var(--tab-accent, var(--teal)); color:var(--ink); }

/* subject overview */
.overview-panel{
  margin:0 48px 22px; padding:20px 24px; background:var(--ink-2); border:1px solid var(--line);
  border-left:3px solid var(--panel-accent, var(--teal)); border-radius:10px; transition:border-color .2s ease;
}
@media (max-width:700px){ .overview-panel{ margin:0 20px 22px; } }
.overview-panel h3{ font-family:'Space Grotesk',sans-serif; font-size:18px; margin:0 0 6px; font-weight:600; display:flex; gap:10px; align-items:baseline;}
.overview-panel h3 .code{ font-family:'IBM Plex Mono',monospace; font-size:11.5px; color:var(--panel-accent, var(--teal)); }
.overview-panel p{ color:var(--paper-dim); font-size:13.5px; line-height:1.65; margin:0; max-width:64ch;}
.overview-meta{ display:flex; gap:16px; flex-wrap:wrap; margin-top:12px; font-family:'IBM Plex Mono',monospace; font-size:11.5px; color:var(--slate);}
.overview-meta b{ color:var(--paper-dim); font-weight:500;}

/* theory / practical tabs */
.cat-tabs{ display:flex; padding:0 48px; margin-bottom:18px;}
@media (max-width:700px){ .cat-tabs{ padding:0 20px; } }
.cat-tab{
  font-family:'IBM Plex Mono',monospace; font-size:12.5px; font-weight:500; color:var(--paper-dim);
  background:transparent; border:1px solid var(--line); padding:9px 20px; cursor:pointer; transition:.2s ease;
}
.cat-tab:first-child{ border-radius:8px 0 0 8px; }
.cat-tab:last-child{ border-radius:0 8px 8px 0; border-left:none; }
.cat-tab[aria-selected="true"]{ background:var(--panel-accent, var(--teal)); border-color:var(--panel-accent, var(--teal)); color:var(--ink); font-weight:600;}
.cat-tab:not([aria-selected="true"]):hover{ color:var(--paper); }

/* chapter directory */
.doc-panel{ padding:0 48px 56px;}
@media (max-width:700px){ .doc-panel{ padding:0 20px 40px; } }
.doc-list{ list-style:none; margin:0; padding:0; border-top:1px solid var(--line);}
.doc-row{
  display:flex; align-items:center; gap:14px; padding:13px 2px 13px 10px;
  border-bottom:1px solid var(--line); border-left:2px solid transparent;
  transition:border-color .2s ease;
}
.doc-row:hover, .doc-row:focus-within{ border-left-color:var(--panel-accent, var(--teal)); }
.doc-tag{
  font-family:'IBM Plex Mono',monospace; font-size:11.5px; font-weight:600; color:var(--panel-accent, var(--teal));
  background:var(--ink-2); border:1px solid var(--line); border-radius:6px; width:34px; height:34px; flex:none;
  display:flex; align-items:center; justify-content:center;
}
.doc-main{ flex:1; min-width:0; display:flex; align-items:baseline; gap:10px; overflow:hidden;}
.doc-title{ font-size:13.5px; color:var(--paper); white-space:nowrap; overflow:hidden; text-overflow:ellipsis;}
.doc-leader{ flex:1; min-width:20px; height:0; border-bottom:1px dotted var(--line); transform:translateY(-4px);}
.doc-kind{ font-family:'IBM Plex Mono',monospace; font-size:10.5px; color:var(--slate); flex:none;}
.doc-actions{ display:flex; gap:6px; flex:none;}
.doc-icon{
  width:32px; height:32px; display:flex; align-items:center; justify-content:center; border-radius:7px;
  border:1px solid var(--line); background:var(--ink-2); color:var(--paper-dim); text-decoration:none; transition:.2s ease;
}
.doc-icon:hover{ color:var(--panel-accent, var(--teal)); border-color:var(--panel-accent, var(--teal)); }
.doc-icon svg{ width:15px; height:15px; display:block; }
.doc-empty{ padding:28px 2px; font-family:'IBM Plex Mono',monospace; color:var(--slate); font-size:13px;}

/* loading skeleton */
.doc-row.is-skeleton .doc-tag,
.doc-row.is-skeleton .doc-title,
.doc-row.is-skeleton .doc-icon{
  background:linear-gradient(90deg, var(--ink-2) 25%, rgba(237,234,224,0.08) 37%, var(--ink-2) 63%);
  background-size:400% 100%; animation:doc-shimmer 1.4s ease infinite; color:transparent; border-color:var(--line);
}
.doc-row.is-skeleton .doc-title{ height:11px; width:55%; border-radius:4px; }
.doc-row.is-skeleton .doc-leader,
.doc-row.is-skeleton .doc-kind{ opacity:0; }
@keyframes doc-shimmer{ 0%{background-position:200% 0;} 100%{background-position:-200% 0;} }
@media (prefers-reduced-motion: reduce){
  .doc-row.is-skeleton .doc-tag, .doc-row.is-skeleton .doc-title, .doc-row.is-skeleton .doc-icon{ animation:none; }
}

/* exam archive strip */
.archive-wrap{ padding:0 48px 56px;}
@media (max-width:700px){ .archive-wrap{ padding:0 20px 40px; } }
.archive-wrap .card{ display:flex; align-items:center; justify-content:space-between; gap:18px; flex-wrap:wrap;}
.archive-wrap .card > div:first-child{ flex:1; min-width:220px; }

@media (max-width:700px){
  .doc-row{ flex-wrap:wrap; }
  .doc-main{ order:3; flex-basis:100%; margin-top:6px; }
  .doc-leader, .doc-kind{ display:none; }
}

/* ===== contact ===== */
.contact-wrap{ padding:80px 48px; display:flex; flex-direction:column; align-items:flex-start; max-width:640px;}
@media (max-width:700px){ .contact-wrap{padding:48px 24px;} }
.contact-wrap h2{font-family:'Space Grotesk',sans-serif; font-size:34px; margin-bottom:14px;}
.contact-wrap p{color:var(--paper-dim); line-height:1.8; font-size:15px; margin-bottom:30px;}
.contact-box{
  font-family:'IBM Plex Mono',monospace; background:var(--ink-2); border:1px solid var(--line);
  border-radius:10px; padding:22px 26px; width:100%; margin-bottom:14px; display:flex; justify-content:space-between; align-items:center;
  gap:12px; flex-wrap:wrap;
}
.contact-box .k{color:var(--slate); font-size:11px;}
.contact-box .v{color:var(--teal); font-size:14px; margin-top:4px; word-break:break-all;}

footer{ padding:26px 48px; border-top:1px solid var(--line); font-family:'IBM Plex Mono',monospace; font-size:11px; color:var(--slate); text-align:center;}

.reveal{opacity:0; transform:translateY(10px); transition:opacity 0.5s ease, transform 0.5s ease;}
.reveal.show{opacity:1; transform:translateY(0);}