:root{--bg:#071017;--panel:#0b1821;--ink:#e9f1f5;--muted:#8fa4b2;--line:#223642;--cyan:#7dd8ff;--max:1120px}

*{box-sizing:border-box}

html{scroll-behavior:smooth}

body{
    margin:0;
    background:var(--bg);
    color:var(--ink);
    font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
    line-height:1.75
}

::selection{
    background:#79d8ff;
    color:#071017
}

.skip{
    position:fixed;
    left:1rem;
    top:-5rem;
    z-index:99;
    background:white;
    color:#000;
    padding:.7rem 1rem
}

.skip:focus{top:1rem}

/* =========================================================
   HERO
   Preserve the complete source image at every viewport size.
   No cropping. No forced viewport-relative image height.
   ========================================================= */

.hero{
    position:relative;
    width:100%;
    background:#09151d;
    overflow:hidden
}

.hero img{
    display:block;
    width:100%;
    max-width:100%;
    height:auto;
    min-height:0;
    object-fit:contain;
    object-position:center
}

.hero-fade{
    position:absolute;
    inset:auto 0 0;
    height:22%;
    background:linear-gradient(transparent,var(--bg));
    pointer-events:none
}

.hero-accessible-title{
    position:absolute;
    width:1px;
    height:1px;
    overflow:hidden;
    clip:rect(0 0 0 0)
}

/* ========================================================= */

.rail{
    position:sticky;
    top:0;
    z-index:30;
    border-block:1px solid rgba(125,216,255,.16);
    background:rgba(7,16,23,.9);
    backdrop-filter:blur(18px)
}

.rail-inner{
    max-width:var(--max);
    margin:auto;
    min-height:56px;
    padding:0 24px;
    display:flex;
    align-items:center;
    gap:2rem
}

.brand{
    color:var(--ink);
    font-weight:800;
    letter-spacing:.16em;
    text-decoration:none
}

.brand span{color:var(--cyan)}

.toc{
    margin-left:auto;
    display:flex;
    gap:1.3rem
}

.toc a,.toc-toggle{
    font:600 11px/1 system-ui;
    letter-spacing:.14em;
    color:var(--muted);
    text-decoration:none;
    background:none;
    border:0
}

.toc a:hover{color:var(--cyan)}

.toc-toggle{
    display:none;
    margin-left:auto
}

.article{
    max-width:var(--max);
    margin:auto;
    padding:0 24px
}

.mast{
    padding:8rem 0 7rem;
    max-width:920px
}

.eyebrow,.kicker,.meta{
    font-size:.72rem;
    letter-spacing:.22em;
    text-transform:uppercase;
    color:var(--cyan)
}

.lede{
    font-size:clamp(1.7rem,3.4vw,3.1rem);
    line-height:1.22;
    letter-spacing:-.025em;
    margin:1.2rem 0 3rem
}

.meta{
    display:flex;
    flex-wrap:wrap;
    gap:1.3rem;
    color:var(--muted)
}

code{
    font-family:"SFMono-Regular",Consolas,monospace;
    color:#a8e7ff
}

.chapter{
    display:grid;
    grid-template-columns:100px 1fr;
    gap:2rem;
    padding:8rem 0;
    border-top:1px solid var(--line);
    scroll-margin-top:70px
}

.chapter-no{
    font:300 3.6rem/1 ui-monospace,monospace;
    color:#29404d
}

.chapter-body{max-width:820px}

.chapter h2{
    font-size:clamp(2.2rem,5vw,4.6rem);
    line-height:1.02;
    letter-spacing:-.045em;
    margin:.6rem 0 2.2rem
}

.chapter p{
    font-size:1.1rem;
    color:#bdcbd3;
    max-width:74ch
}

.chapter blockquote{
    margin:3rem 0;
    padding:1.5rem 0 1.5rem 2rem;
    border-left:2px solid var(--cyan);
    font-size:clamp(1.3rem,2.5vw,2rem);
    line-height:1.35;
    color:var(--ink)
}

.terminal{
    margin:2.8rem 0;
    padding:1.4rem 1.6rem;
    border:1px solid var(--line);
    background:#050b0f;
    font:14px/1.9 "SFMono-Regular",Consolas,monospace;
    color:#9fb2bd;
    overflow:auto
}

.terminal span{color:var(--cyan)}

.equation{
    font:clamp(2rem,6vw,5.5rem)/1.1 Georgia,serif;
    text-align:center;
    padding:4rem 1rem;
    margin:3rem 0;
    border-block:1px solid var(--line);
    color:#dff6ff
}

.thesis{
    margin:3rem 0;
    padding:2rem;
    border:1px solid rgba(125,216,255,.35);
    background:linear-gradient(135deg,rgba(125,216,255,.08),transparent);
    font-size:1.35rem
}

.thesis span{
    display:block;
    margin-bottom:.8rem;
    font:700 .7rem/1 system-ui;
    letter-spacing:.2em;
    color:var(--cyan)
}

.flow{
    display:flex;
    align-items:center;
    flex-wrap:wrap;
    gap:.65rem;
    margin:3rem 0
}

.flow span{
    padding:.65rem .85rem;
    border:1px solid var(--line);
    font:12px/1.2 ui-monospace,monospace;
    text-transform:uppercase;
    letter-spacing:.08em
}

.flow i{
    color:var(--cyan);
    font-style:normal
}

.ledger{
    display:grid;
    grid-template-columns:repeat(2,1fr);
    gap:1px;
    background:var(--line);
    border:1px solid var(--line);
    margin-top:3rem
}

.ledger article{
    background:var(--panel);
    padding:2rem
}

.ledger b{
    font-size:.65rem;
    letter-spacing:.2em;
    color:var(--cyan)
}

.ledger h3{
    font-size:1.35rem;
    margin:.5rem 0
}

.ledger article p{
    font-size:.95rem;
    margin:0
}

.final{padding-bottom:10rem}

.closing{
    margin-top:4rem!important;
    font-size:clamp(1.5rem,3vw,2.6rem)!important;
    line-height:1.35;
    color:var(--ink)!important
}

.closing strong{color:var(--cyan)}

footer{
    border-top:1px solid var(--line);
    padding:3rem 0 5rem;
    display:flex;
    justify-content:space-between;
    gap:2rem;
    color:var(--muted);
    font-size:.7rem;
    letter-spacing:.16em;
    line-height:1.8
}

footer strong{color:var(--ink)}

footer a{
    color:var(--cyan);
    text-decoration:none
}

@media(max-width:820px){

    /* Preserve complete 16:9 hero on mobile as well. */
    .hero{
        min-height:0
    }

    .hero img{
        width:100%;
        max-width:100%;
        height:auto;
        min-height:0;
        object-fit:contain
    }

    .toc-toggle{display:block}

    .toc{
        display:none;
        position:absolute;
        left:0;
        right:0;
        top:56px;
        padding:1rem 24px 1.5rem;
        background:rgba(7,16,23,.98);
        border-bottom:1px solid var(--line);
        flex-direction:column
    }

    .toc.open{display:flex}

    .mast{padding:5rem 0}

    .chapter{
        grid-template-columns:1fr;
        padding:5rem 0
    }

    .chapter-no{font-size:1.4rem}

    .ledger{grid-template-columns:1fr}

    footer{flex-direction:column}
}

@media(prefers-reduced-motion:reduce){
    html{scroll-behavior:auto}
}