:root {
  --primary: #2563eb;
  --primary-light: #60a5fa;
  --primary-dark: #1d4ed8;
  --accent: #fbbf24;
  --success: #10b981;
  --danger: #ef4444;
  --info: #06b6d4;
  --bg: #0f172a;
  --surface: #1e293b;
  --surface2: #273449;
  --border: #334155;
  --text: #e2e8f0;
  --text-muted: #b6c4d6;
  --text-dim: #94a3b8;
  --code-bg: #0d1117;
  --radius: 10px;
  --shadow: 0 4px 20px rgba(0,0,0,0.4);
}
*{box-sizing:border-box;margin:0;padding:0}
body{font-family:'Segoe UI',system-ui,-apple-system,sans-serif;background:var(--bg);color:var(--text);line-height:1.7;font-size:16px}
.layout{display:grid;grid-template-columns:260px 1fr;min-height:100vh}
.sidebar{background:var(--surface);border-right:1px solid var(--border);padding:1.5rem 0;position:sticky;top:0;height:100vh;overflow-y:auto}
.sidebar-header{padding:0 1.5rem 1.5rem;border-bottom:1px solid var(--border);margin-bottom:1rem}
.sidebar-header h2{font-size:1rem;color:var(--primary-light);font-weight:700;letter-spacing:.05em;text-transform:uppercase}
.sidebar-header p{font-size:.78rem;color:var(--text-dim);margin-top:.2rem}
.sidebar a{display:flex;align-items:center;gap:.7rem;padding:.6rem 1.5rem;color:var(--text-muted);text-decoration:none;font-size:.875rem;transition:all .15s;border-left:3px solid transparent}
.sidebar a:hover{background:var(--surface2);color:var(--text);border-left-color:var(--primary)}
.sidebar a.active{background:rgba(37,99,235,.15);color:var(--primary-light);border-left-color:var(--primary);font-weight:600}
.sidebar .day-num{background:var(--surface2);color:var(--text-dim);font-size:.7rem;font-weight:700;padding:.15rem .4rem;border-radius:4px;min-width:28px;text-align:center}
.sidebar a.active .day-num{background:var(--primary);color:white}
.content{padding:2.5rem 3rem;max-width:1000px}
h1{font-size:2rem;color:var(--text);margin-bottom:.3rem}
h2{font-size:1.4rem;color:var(--text);margin:2.5rem 0 1rem;padding-bottom:.5rem;border-bottom:2px solid var(--border)}
h3{font-size:1.1rem;color:var(--primary-light);margin:1.5rem 0 .6rem}
h4{font-size:.95rem;color:var(--accent);margin:1rem 0 .4rem;text-transform:uppercase;letter-spacing:.05em}
p{color:var(--text-muted);margin-bottom:.8rem}
strong{color:var(--text)}
.page-header{margin-bottom:2rem;padding-bottom:1.5rem;border-bottom:1px solid var(--border)}
.page-header .day-badge{display:inline-block;background:var(--primary);color:white;font-size:.75rem;font-weight:700;padding:.2rem .7rem;border-radius:20px;margin-bottom:.5rem;letter-spacing:.05em;text-transform:uppercase}
.page-header p{font-size:1.1rem;color:var(--text-muted);margin-top:.5rem}
.callout{border-radius:var(--radius);padding:1.2rem 1.5rem;margin:1.5rem 0;border-left:4px solid}
.callout-label{display:flex;align-items:center;gap:.5rem;font-size:.8rem;font-weight:700;text-transform:uppercase;letter-spacing:.07em;margin-bottom:.5rem}
.callout-label .icon{font-size:1rem}
.callout p{margin-bottom:0;font-size:.95rem}
.callout.realworld{background:rgba(16,185,129,.07);border-color:var(--success)}
.callout.realworld .callout-label{color:var(--success)}
.callout.tip{background:rgba(6,182,212,.07);border-color:var(--info)}
.callout.tip .callout-label{color:var(--info)}
.callout.warning{background:rgba(239,68,68,.07);border-color:var(--danger)}
.callout.warning .callout-label{color:var(--danger)}
.callout.story{background:rgba(37,99,235,.07);border-color:var(--primary)}
.callout.story .callout-label{color:var(--primary-light)}
pre{padding:1.2rem 1.5rem;overflow-x:auto;margin:1rem 0;font-size:.875rem;line-height:1.7;font-family:'Cascadia Code','Fira Code',Consolas,monospace;background:var(--code-bg);border:1px solid var(--border);border-radius:var(--radius);color:#c9d1d9}
code{color:#e2e8f0}
p code,li code,td code{background:var(--surface2);color:var(--primary-light);font-size:.85em;padding:.1em .4em;border-radius:4px;font-family:Consolas,monospace}
.breadcrumb{display:flex;align-items:center;gap:.5rem;font-size:.8rem;color:var(--text-dim);margin-bottom:1.5rem}
.breadcrumb a{color:var(--primary-light);text-decoration:none}
.breadcrumb a:hover{text-decoration:underline}
.day-nav{display:flex;justify-content:space-between;margin-top:3rem;padding-top:1.5rem;border-top:1px solid var(--border)}
.day-nav a{display:flex;flex-direction:column;gap:.2rem;padding:.8rem 1.2rem;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);text-decoration:none;transition:all .15s;max-width:200px}
.day-nav a:hover{border-color:var(--primary);background:var(--surface2)}
.nav-label{font-size:.75rem;color:var(--text-dim);text-transform:uppercase;letter-spacing:.05em}
.nav-title{font-size:.9rem;color:var(--text);font-weight:600}
.cheat-sheet{background:linear-gradient(135deg,rgba(16,185,129,.06) 0%,rgba(6,182,212,.05) 100%);border:1px solid rgba(16,185,129,.3);border-radius:var(--radius);padding:1.4rem 1.6rem;margin:2rem 0}
.cheat-sheet h3{font-size:1rem;color:#10b981;margin:0 0 1rem}
/* Hour bar */
.hour-bar{display:flex;gap:0;margin:1.2rem 0 1.8rem;border-radius:10px;overflow:hidden;border:1px solid var(--border)}
.hour-slot{flex:1;padding:.55rem .4rem;text-align:center;font-size:.68rem;font-weight:700;line-height:1.3}
.hs-hook{background:rgba(245,158,11,.15);color:#f59e0b}
.hs-concept{background:rgba(37,99,235,.15);color:var(--primary-light)}
.hs-hands{background:rgba(34,197,94,.15);color:#4ade80}
.hs-try{background:rgba(6,182,212,.15);color:#22d3ee}
.hs-wrap{background:rgba(168,85,247,.15);color:#c084fc}
/* Hook / Try boxes */
.hook-box{background:linear-gradient(135deg,rgba(245,158,11,.08),rgba(245,158,11,.03));border:1px solid rgba(245,158,11,.25);border-radius:var(--radius);padding:1.2rem 1.4rem;margin:1rem 0}
.hook-box .hook-label{font-size:.68rem;font-weight:800;text-transform:uppercase;letter-spacing:.08em;color:#f59e0b;margin-bottom:.5rem}
.hook-box p{color:var(--text-muted);font-size:.9rem;line-height:1.7}
.try-box{background:rgba(6,182,212,.06);border:1px solid rgba(6,182,212,.25);border-radius:var(--radius);padding:1.2rem 1.4rem;margin:1rem 0}
.try-box .try-label{font-size:.68rem;font-weight:800;text-transform:uppercase;letter-spacing:.08em;color:#22d3ee;margin-bottom:.6rem}
.try-box ol{color:var(--text-muted);font-size:.88rem;line-height:1.8;padding-left:1.2rem}
/* CS grid */
.cs-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:1rem;margin-top:.8rem}
.cs-card{background:var(--surface2);border:1px solid var(--border);border-radius:var(--radius);padding:1rem 1.1rem}
.cs-card h4{font-size:.8rem;font-weight:800;text-transform:uppercase;letter-spacing:.05em;color:var(--primary-light);margin-bottom:.6rem}
.cs-card table{width:100%;border-collapse:collapse;font-size:.76rem}
.cs-card td{padding:.25rem .3rem;border-bottom:1px solid rgba(51,65,85,.4);color:var(--text-muted);vertical-align:top}
.cs-card td:first-child{color:var(--text);font-family:Consolas,monospace;font-size:.73rem;white-space:nowrap;padding-right:.6rem}
.cs-card tr:last-child td{border-bottom:none}
/* Big-O pills */
.big-o{display:inline-block;padding:.15rem .55rem;border-radius:999px;font-family:Consolas,monospace;font-size:.78rem;font-weight:700;margin:0 .15rem}
.o1{background:rgba(34,197,94,.15);color:#4ade80}
.on{background:rgba(239,68,68,.15);color:#f87171}
.ologn{background:rgba(245,158,11,.15);color:#fbbf24}
/* Tradeoff */
.tradeoff-grid{display:grid;grid-template-columns:1fr 1fr;gap:1rem;margin:1rem 0}
.tradeoff-box{border-radius:var(--radius);padding:1rem 1.1rem;font-size:.84rem}
.tb-fast{background:rgba(34,197,94,.07);border:1px solid rgba(34,197,94,.25)}
.tb-slow{background:rgba(239,68,68,.07);border:1px solid rgba(239,68,68,.25)}
.tb-label{font-size:.65rem;font-weight:800;text-transform:uppercase;letter-spacing:.07em;margin-bottom:.5rem}
.tb-fast .tb-label{color:#4ade80}
.tb-slow .tb-label{color:#f87171}
.tb-fast p,.tb-slow p{color:var(--text-muted);line-height:1.6;margin:0}
/* Memory bars */
.mem-bar{display:flex;height:32px;border-radius:6px;overflow:hidden;margin:.5rem 0;font-size:.72rem;font-weight:700}
.mem-seg{display:flex;align-items:center;justify-content:center;padding:0 .4rem;white-space:nowrap}
.mem-used{background:rgba(37,99,235,.4);color:#93c5fd}
.mem-extra{background:rgba(168,85,247,.3);color:#c084fc;border-left:1px dashed rgba(168,85,247,.5)}
.mem-label{font-size:.7rem;color:var(--text-muted);margin-top:.2rem}
/* Story rows */
.story-row{display:flex;gap:1rem;align-items:flex-start;margin:.7rem 0}
.story-icon{font-size:1.3rem;flex-shrink:0;margin-top:.1rem}
.story-body{flex:1;color:var(--text-muted);font-size:.88rem;line-height:1.6}
.story-body strong{color:var(--text)}
/* Responsive */
@media(max-width:900px){.layout{grid-template-columns:1fr}.sidebar{display:none}.content{padding:1.5rem}}