:root{
  --bone-black:#0A0908; --bone-white:#EFE9DC; --marrow-red:#6B0F1A; --marrow-red-glow:#8B1828;
  --marrow-ember:#E08894; --steel:#475569; --steel-light:#B8C5D6; --ash:#2A2A28; --panel:#15110f;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bone-black);color:var(--bone-white);
  font:18px/1.7 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif}
a{color:var(--marrow-ember)} a:hover{color:var(--bone-white)}
.skip{position:absolute;left:-999px}.skip:focus{left:8px;top:8px;background:var(--marrow-red);color:#fff;padding:8px 12px;border-radius:6px;z-index:20}
header.top{position:sticky;top:0;z-index:10;background:rgba(10,9,8,.95);border-bottom:1px solid var(--ash);
  padding:12px 18px;display:flex;align-items:center;justify-content:space-between;gap:10px;flex-wrap:wrap}
.brand{font-weight:800;letter-spacing:.14em;text-transform:uppercase;font-size:14px;text-decoration:none;color:var(--bone-white)}
.brand .dot{color:var(--marrow-red-glow)}
nav.menu a{color:var(--steel-light);text-decoration:none;font-size:14px;margin-left:16px;font-weight:600}
nav.menu a:hover,nav.menu a.active{color:var(--bone-white)}
main{max-width:760px;margin:0 auto;padding:30px 20px 90px}
h1{font-size:30px;line-height:1.2;margin:.2em 0 .3em}
h2{font-size:22px;margin:1.4em 0 .4em}
.lead{font-size:19px;color:var(--steel-light)}
.notice{background:#1a1310;border-left:3px solid var(--marrow-red);border-radius:8px;padding:12px 16px;
  color:var(--steel-light);font-size:15px;margin:18px 0}
.btn{display:inline-block;background:var(--marrow-red);color:#fff;text-decoration:none;font-weight:700;
  padding:13px 22px;border-radius:10px;margin:6px 8px 6px 0}
.btn:hover{background:var(--marrow-red-glow);color:#fff}
.btn.ghost{background:transparent;border:1px solid var(--ash);color:var(--bone-white)}
.steps{list-style:none;padding:0;margin:18px 0}
.steps li{background:var(--panel);border:1px solid var(--ash);border-radius:10px;padding:14px 18px;margin:10px 0}
.steps b{color:var(--marrow-ember)}
/* lesson cards */
.lesson{background:var(--panel);border:1px solid var(--ash);border-radius:14px;padding:20px 22px;margin:18px 0}
.lesson h3{margin:0 0 10px;font-size:20px;color:var(--bone-white)}
.lesson p{margin:.45em 0}
.lesson .k{color:var(--marrow-ember);font-weight:700}
.lesson .src{font-size:13px;color:var(--steel)}
.lesson .src a{color:var(--steel-light)}
.progress{font-size:13px;color:var(--steel-light);margin:0 0 6px}
/* glossary */
.gloss{list-style:none;padding:0;margin:0}
.gloss li{padding:12px 0;border-bottom:1px solid var(--ash)}
.gloss .term{color:var(--marrow-ember);font-weight:700}
.jump{font-size:14px;color:var(--steel-light);margin:10px 0 20px;line-height:2}
.jump a{margin-right:8px}
/* deep dive rendered content */
.doc h2{border-top:1px solid var(--ash);padding-top:.5em;margin-top:1.6em}
.doc h3{color:var(--marrow-ember);font-size:18px}
.doc h4{color:var(--steel-light);font-size:15px}
.doc hr{border:0;border-top:1px solid var(--ash);margin:1.4em 0}
.doc ul{padding-left:1.2em}
/* cockpit */
.card{background:var(--panel);border:1px solid var(--ash);border-radius:12px;padding:18px 20px;margin:16px 0}
.check li{display:flex;gap:10px;align-items:flex-start;margin:.5em 0;list-style:none}
.check{padding:0}
.check input{margin-top:4px;accent-color:var(--marrow-red);width:18px;height:18px}
label{display:block;font-size:13px;color:var(--steel-light);margin:8px 0 3px}
input[type=text],input[type=date],textarea{width:100%;background:#0d0b0a;border:1px solid var(--ash);
  color:var(--bone-white);border-radius:8px;padding:9px 11px;font:inherit;font-size:15px}
textarea{min-height:50px}
.row{display:grid;grid-template-columns:1fr 1fr;gap:10px}
button{background:var(--marrow-red);color:#fff;border:0;border-radius:9px;padding:10px 16px;font:inherit;font-weight:700;cursor:pointer;margin-top:10px}
button:hover{background:var(--marrow-red-glow)}
button.ghost{background:transparent;border:1px solid var(--ash);color:var(--steel-light)}
table{width:100%;border-collapse:collapse;margin-top:10px;font-size:14px}
th,td{text-align:left;padding:7px 8px;border-bottom:1px solid var(--ash);vertical-align:top}
th{color:var(--steel-light)}
code{background:#0d0b0a;border:1px solid var(--ash);border-radius:5px;padding:1px 6px;font-size:14px}
footer{max-width:760px;margin:0 auto;padding:20px;color:var(--steel);font-size:13px;border-top:1px solid var(--ash)}
@media (max-width:600px){main{padding:22px 16px 70px}.row{grid-template-columns:1fr}body{font-size:17px}}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{transition:none!important}}