:root{--bg-0: oklch(.15 .012 60);--bg-1: oklch(.19 .015 60);--bg-2: oklch(.23 .018 60);--fg-0: oklch(.97 .01 80);--fg-1: oklch(.82 .015 70);--fg-2: oklch(.62 .02 70);--fg-3: oklch(.45 .02 70);--gold: oklch(.82 .14 78);--gold-soft: oklch(.82 .14 78 / .15);--cyan: oklch(.78 .13 215);--cyan-soft: oklch(.78 .13 215 / .15);--violet: oklch(.72 .15 290);--violet-soft: oklch(.72 .15 290 / .15);--glass-bg: oklch(.25 .02 70 / .35);--glass-border: oklch(.85 .02 80 / .12);--glass-border-strong: oklch(.85 .02 80 / .2);--font-display: "Instrument Serif", "Times New Roman", serif;--font-ui: "Geist", system-ui, sans-serif;--font-mono: "JetBrains Mono", ui-monospace, monospace;--r-sm: 8px;--r-md: 14px;--r-lg: 22px;--r-xl: 32px}*{box-sizing:border-box;margin:0;padding:0}html,body{background:var(--bg-0);color:var(--fg-0);font-family:var(--font-ui);font-size:16px;line-height:1.5;-webkit-font-smoothing:antialiased;min-height:100vh}body{background:radial-gradient(ellipse 80% 60% at 80% -10%,oklch(.82 .14 78 / .12),transparent 60%),radial-gradient(ellipse 60% 50% at 10% 110%,oklch(.78 .13 215 / .1),transparent 60%),var(--bg-0);background-attachment:fixed}h1,h2,h3{font-family:var(--font-display);font-weight:400;letter-spacing:-.01em;line-height:1.05}.mono{font-family:var(--font-mono);font-feature-settings:"tnum"}.nav{position:sticky;top:0;z-index:50;display:flex;align-items:center;justify-content:space-between;padding:18px 32px;background:#0f0a0699;backdrop-filter:blur(18px) saturate(1.4);-webkit-backdrop-filter:blur(18px) saturate(1.4);border-bottom:1px solid var(--glass-border)}.nav-brand{display:flex;align-items:center;gap:10px;font-family:var(--font-display);font-size:22px;color:var(--fg-0);text-decoration:none}.nav-brand .mark{width:28px;height:28px;border-radius:8px;background:linear-gradient(135deg,var(--gold),oklch(.68 .16 50));display:grid;place-items:center;color:var(--bg-0);font-family:var(--font-display);font-size:18px;font-style:italic}.nav-links{display:flex;align-items:center;gap:8px;font-size:14px}.nav-links a{color:var(--fg-1);text-decoration:none;padding:8px 14px;border-radius:999px;transition:all .2s}.nav-links a:hover{color:var(--fg-0);background:var(--glass-bg)}.lang-toggle{display:inline-flex;padding:4px;background:var(--bg-2);border-radius:999px;border:1px solid var(--glass-border);font-size:12px;font-family:var(--font-mono)}.lang-toggle button{background:transparent;border:none;color:var(--fg-2);padding:5px 12px;border-radius:999px;cursor:pointer;font-family:inherit;text-transform:uppercase;letter-spacing:.05em;transition:all .2s}.lang-toggle button.active{background:var(--fg-0);color:var(--bg-0)}.btn{display:inline-flex;align-items:center;gap:8px;padding:12px 22px;border-radius:999px;font-family:var(--font-ui);font-size:14px;font-weight:500;text-decoration:none;cursor:pointer;border:1px solid transparent;transition:all .2s}.btn-primary{background:var(--fg-0);color:var(--bg-0)}.btn-primary:hover{background:var(--gold)}.btn-ghost{background:var(--glass-bg);color:var(--fg-0);border-color:var(--glass-border-strong);backdrop-filter:blur(12px)}.btn-ghost:hover{background:var(--bg-2)}.glass{background:var(--glass-bg);backdrop-filter:blur(22px) saturate(1.3);-webkit-backdrop-filter:blur(22px) saturate(1.3);border:1px solid var(--glass-border);border-radius:var(--r-lg)}.slider-row{display:flex;flex-direction:column;gap:8px;padding:14px 18px;background:var(--bg-1);border-radius:var(--r-md);border:1px solid var(--glass-border)}.slider-label{display:flex;justify-content:space-between;align-items:baseline;font-size:13px;color:var(--fg-2);font-family:var(--font-mono);text-transform:uppercase;letter-spacing:.06em}.slider-label .val{color:var(--gold);font-size:15px;text-transform:none;letter-spacing:0}input[type=range]{-webkit-appearance:none;width:100%;height:4px;background:var(--bg-2);border-radius:999px;outline:none}input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:18px;height:18px;border-radius:50%;background:var(--gold);cursor:pointer;box-shadow:0 0 0 4px #f6b84d26;transition:box-shadow .15s}input[type=range]::-webkit-slider-thumb:hover{box-shadow:0 0 0 7px #f6b84d33}input[type=range]::-moz-range-thumb{width:18px;height:18px;border-radius:50%;background:var(--gold);cursor:pointer;border:none}.tag{display:inline-flex;align-items:center;gap:6px;font-family:var(--font-mono);font-size:11px;text-transform:uppercase;letter-spacing:.08em;color:var(--fg-2);padding:5px 10px;border-radius:999px;background:var(--bg-2);border:1px solid var(--glass-border)}.tag .dot{width:6px;height:6px;border-radius:50%;background:var(--gold)}.tag.cyan .dot{background:var(--cyan)}.tag.violet .dot{background:var(--violet)}.lesson{max-width:1320px;margin:0 auto;padding:48px 32px 120px}.lesson-header{display:flex;flex-direction:column;gap:20px;margin-bottom:36px}.breadcrumb{display:flex;align-items:center;gap:10px;font-size:13px;color:var(--fg-2);font-family:var(--font-mono)}.breadcrumb a{color:var(--fg-2);text-decoration:none}.breadcrumb a:hover{color:var(--fg-0)}.lesson-title{font-size:clamp(40px,6vw,72px);max-width:900px}.lesson-title em{color:var(--gold);font-style:italic}.lesson-intro{font-size:19px;color:var(--fg-1);max-width:680px;line-height:1.55}.lesson-grid{display:grid;grid-template-columns:1.3fr 1fr;gap:22px}@media(max-width:960px){.lesson-grid{grid-template-columns:1fr}}.stage{position:relative;padding:28px;min-height:520px;overflow:hidden}.panel{padding:26px;display:flex;flex-direction:column;gap:18px}.panel h3{font-family:var(--font-ui);font-size:13px;font-weight:500;color:var(--fg-2);text-transform:uppercase;letter-spacing:.1em}.formula{font-family:var(--font-display);font-size:42px;line-height:1;color:var(--fg-0);padding:22px 20px;background:linear-gradient(180deg,var(--bg-1),var(--bg-0));border-radius:var(--r-md);border:1px solid var(--glass-border);text-align:center;letter-spacing:.02em}.formula .gold{color:var(--gold)}.formula .cyan{color:var(--cyan)}.formula .violet{color:var(--violet)}.metric-row{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.metric{padding:14px 16px;background:var(--bg-1);border-radius:var(--r-md);border:1px solid var(--glass-border)}.metric .k{font-family:var(--font-mono);font-size:11px;color:var(--fg-2);text-transform:uppercase;letter-spacing:.08em;margin-bottom:6px}.metric .v{font-family:var(--font-mono);font-size:20px;color:var(--fg-0);font-variant-numeric:tabular-nums}.prose{color:var(--fg-1);line-height:1.65;font-size:15px}.prose+.prose{margin-top:12px}.prose em{color:var(--gold);font-style:normal}.prose code{font-family:var(--font-mono);background:var(--bg-2);padding:2px 6px;border-radius:4px;font-size:13px;color:var(--fg-0)}.segment{display:inline-flex;padding:4px;background:var(--bg-2);border-radius:999px;border:1px solid var(--glass-border);font-size:12px;font-family:var(--font-mono)}.segment button{background:transparent;border:none;color:var(--fg-2);padding:7px 14px;border-radius:999px;cursor:pointer;text-transform:uppercase;letter-spacing:.06em;font-family:inherit;transition:all .2s}.segment button.active{background:var(--gold);color:var(--bg-0)}.lesson-nav{display:flex;justify-content:space-between;gap:16px;margin-top:60px;padding-top:30px;border-top:1px solid var(--glass-border)}.lesson-nav a{flex:1;padding:18px 22px;background:var(--bg-1);border:1px solid var(--glass-border);border-radius:var(--r-md);text-decoration:none;color:var(--fg-0);display:flex;flex-direction:column;gap:4px;transition:all .2s}.lesson-nav a:hover{background:var(--bg-2);border-color:var(--glass-border-strong)}.lesson-nav a .dir{font-family:var(--font-mono);font-size:11px;color:var(--fg-2);text-transform:uppercase;letter-spacing:.08em}.lesson-nav a .t{font-family:var(--font-display);font-size:22px}.lesson-nav a.next{text-align:right;align-items:flex-end}.row{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.col{display:flex;flex-direction:column;gap:12px}.site-footer{margin-top:80px;padding:56px 64px 48px;border-top:1px solid var(--glass-border);display:flex;flex-direction:column;gap:24px;color:var(--fg-2);font-size:13px;font-family:var(--font-mono)}.site-footer .footer-main{display:flex;justify-content:space-between;align-items:baseline;flex-wrap:wrap;gap:16px 32px}.site-footer .footer-brand{color:var(--fg-1)}.site-footer .footer-credit{display:inline-flex;align-items:baseline;gap:8px;letter-spacing:.04em}.site-footer .footer-link{color:var(--gold);text-decoration:none;font-family:var(--font-display);font-style:italic;font-size:18px;letter-spacing:0;padding-bottom:2px;border-bottom:1px solid oklch(.82 .14 78 / .4);transition:border-color .25s,color .25s}.site-footer .footer-link:hover{color:oklch(.92 .14 78);border-bottom-color:var(--gold)}.site-footer .footer-copy{display:flex;justify-content:space-between;align-items:center;padding-top:18px;border-top:1px solid var(--glass-border);font-size:11px;letter-spacing:.1em;text-transform:uppercase;opacity:.7}@media(max-width:640px){.site-footer{padding:40px 28px 32px}}