:root{--brand:#1f4e79;--brand-d:#163a5b;--accent:#e8f1f8;--ink:#1b1f23;--muted:#4a5560;--line:#c5d5e3;--bg:#fff;--err:#a3201a;--err-bg:#fdecea;--ok:#17603a;--focus:#1d4ed8;--sans:system-ui,-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;--mono:ui-monospace,SFMono-Regular,Menlo,Consolas,"Liberation Mono",monospace}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:17px/1.55 var(--sans)}
a{color:var(--brand)}a:hover{color:var(--brand-d)}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px}
.site-head :focus-visible,.site-foot :focus-visible{outline-color:#fff}
[hidden]{display:none!important}
.wrap{max-width:1040px;margin:0 auto;padding:0 16px}
.skip{position:absolute;left:-999px;top:0;background:#fff;color:var(--ink);padding:10px 14px;z-index:9}.skip:focus{left:8px;top:8px}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.print-brand{display:none}

/* header */
.site-head{background:var(--brand);color:#fff}
.site-head .wrap{display:flex;flex-wrap:wrap;align-items:center;gap:0 18px;padding-top:4px;padding-bottom:2px}
.brand{display:inline-flex;align-items:center;gap:10px;min-height:44px;color:#fff;text-decoration:none;font-weight:700;font-size:1.05rem;line-height:1.2}
.brand:hover{color:#fff}.brand svg{width:30px;height:30px;flex:none}
.nav{display:flex;gap:2px;overflow-x:auto;flex:1 1 100%;scrollbar-width:thin}
.nav a{display:inline-flex;align-items:center;min-height:44px;padding:0 12px;color:#fff;text-decoration:none;white-space:nowrap;font-size:.95rem;border-bottom:3px solid transparent}
.nav a:hover{border-bottom-color:#a9cbe6;color:#fff}
.nav a[aria-current=page]{border-bottom-color:#fff;font-weight:700}
@media (max-width:899px){.nav{padding-right:36px;scroll-padding-inline-end:36px;-webkit-mask-image:linear-gradient(to right,#000 calc(100% - 36px),transparent);mask-image:linear-gradient(to right,#000 calc(100% - 36px),transparent)}}
@media (min-width:900px){.nav{flex:1 1 auto;justify-content:flex-end}.site-head .wrap{padding-top:0;padding-bottom:0}}

main{padding-bottom:36px}
h1,h2,h3{line-height:1.25;color:#0d2536}
h1{font-size:1.65rem;margin:14px 0 6px}
h2{font-size:1.4rem;margin:34px 0 10px}
h3{font-size:1.1rem;margin:20px 0 6px}
@media (min-width:700px){h1{font-size:2.1rem;margin:20px 0 8px}}
.intro{font-size:1.04rem;margin:0 0 14px;max-width:70ch;overflow-wrap:anywhere}
[data-out=splitnote]{overflow-wrap:anywhere}
.crumbs ol{list-style:none;display:flex;flex-wrap:wrap;gap:0 6px;padding:0;margin:6px 0 0;font-size:.9rem;color:var(--muted)}
.crumbs li{display:inline-flex;align-items:center;min-height:32px}
.crumbs li+li::before{content:"\203A";margin-right:6px}
.crumbs a{display:inline-flex;align-items:center;justify-content:center;min-width:44px;min-height:44px}
.last-updated{font-size:.9rem;color:var(--muted);margin:10px 0 0}

/* tool card */
.tool{background:var(--accent);border:1px solid var(--line);border-radius:14px;padding:14px;margin:0 0 8px}
.tool h2{margin-top:0;font-size:1.2rem}
.tool-grid{display:grid;grid-template-columns:minmax(0,1fr);gap:14px}
@media (min-width:900px){.tool-grid.two{grid-template-columns:minmax(0,.9fr) minmax(0,1.1fr);align-items:start}.tool{padding:18px}}
.panel{background:#fff;border:1px solid var(--line);border-radius:12px;padding:12px}
.field{margin:0 0 10px}
.field>label,.lbl{display:block;font-weight:600;font-size:.95rem;margin:0 0 3px}
input[type=text],select,textarea{width:100%;min-height:44px;font:inherit;font-size:1.05rem;padding:8px 10px;border:2px solid #7f98a8;border-radius:8px;background:#fff;color:var(--ink)}
select{padding-right:6px}
input[aria-invalid=true]{border-color:var(--err);background:var(--err-bg)}
.pair{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px}
.pair .field{margin:0}
.err{margin:4px 0 0;padding:6px 10px;color:var(--err);background:var(--err-bg);border-left:4px solid var(--err);border-radius:4px;font-size:.92rem}
.err a{color:var(--err);font-weight:600}
.hint,.note{font-size:.9rem;color:var(--muted);margin:3px 0 0}

.btn{display:inline-flex;align-items:center;justify-content:center;min-height:44px;padding:8px 16px;font:inherit;font-weight:600;border-radius:10px;border:2px solid var(--brand);background:var(--brand);color:#fff;cursor:pointer;text-decoration:none}
.btn:hover{background:var(--brand-d);border-color:var(--brand-d);color:#fff}
.btn.ghost{background:#fff;color:var(--brand)}.btn.ghost:hover{background:var(--accent);color:var(--brand-d)}
.btn.small{min-width:44px;padding:4px 10px;font-size:.88rem}
.actions{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin-top:12px}
.status{font-size:.92rem;color:var(--ok);font-weight:600}
textarea{margin-top:8px;font-size:.95rem}

/* results */
.results{background:#fff;border:1px solid var(--line);border-left:6px solid var(--brand);border-radius:12px;padding:6px 12px}
.hostnote{margin:6px 0;padding:8px 12px;border-left:4px solid var(--brand);background:var(--accent);font-weight:600;font-size:.95rem}
.rows{margin:0}
.row{display:grid;grid-template-columns:minmax(0,9.5rem) minmax(0,1fr) auto;align-items:center;gap:0 10px;min-height:44px;border-bottom:1px solid var(--line)}
.row:last-child{border-bottom:0}
.row dt{font-weight:600;font-size:.88rem;color:var(--muted);line-height:1.25}
.row dd{margin:0}
.v{font-weight:700;font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.row.bin{grid-template-columns:minmax(0,1fr) auto;padding-top:4px}
.row.bin dt{grid-column:1/-1}
.mono{font:600 .8rem/1.35 var(--mono);overflow-wrap:normal}
.net{font-weight:800;text-decoration:underline;text-decoration-thickness:2px;text-underline-offset:2px}
.res-formula,.res-calc{margin:8px 0 6px;color:var(--muted);font-size:.93rem}
.res-calc{margin-top:0;color:var(--ink);font-weight:600}
.ref-line{margin:10px 0 0;font-size:.92rem}
.ref-line a{display:inline-flex;align-items:center;min-height:44px}
.splitbox{margin:12px 0 0}.splitbox h3{margin:0 0 4px;font-size:1rem}
.splitwrap{max-height:22rem;overflow:auto;background:#fff;border:1px solid var(--line);border-radius:8px}
.splitwrap ol{margin:0;padding-left:3em}
.splitwrap li{border-bottom:1px solid var(--line)}.splitwrap li:last-child{border-bottom:0}
.srow{display:flex;align-items:center;justify-content:space-between;gap:8px;min-height:44px;padding-right:8px}
.srow .v{min-width:0;font-weight:600}
.handoff{margin:12px 0 0}.handoff h3{margin:0 0 4px;font-size:1rem}
.handoff ul{list-style:none;margin:0;padding:0}
.handoff a{display:inline-flex;align-items:center;min-height:44px}

/* content */
.tbl{overflow-x:auto;margin:10px 0}
.tbl:focus-visible{outline:3px solid var(--focus)}
table{border-collapse:collapse;width:100%;background:#fff}
th,td{border:1px solid var(--line);padding:7px 10px;text-align:left;vertical-align:top}
th{background:var(--accent)}
caption{caption-side:top;text-align:left;font-weight:700;padding:4px 0}
td.num,th.num{text-align:right;font-variant-numeric:tabular-nums}
.chart{max-height:70vh;overflow:auto}
.chart table{border-collapse:separate;border-spacing:0}
.chart thead th{position:sticky;top:0;z-index:1;box-shadow:0 1px 0 var(--line)}
.chart tr.hl th,.chart tr.hl td{font-weight:800;background:#fff3c4}
.chart tr.hl{outline:3px solid var(--ink);outline-offset:-3px}
.chart-sec h2{margin-top:18px}
.steps{padding-left:1.4em}.steps li{margin:5px 0}
.content ul,.page-content ul{padding-left:1.3em}
.gloss dt{font-weight:700;margin-top:10px}.gloss dd{margin:2px 0 0}
.qa{border-top:1px solid var(--line);padding-top:2px}
.qa h3{margin-top:14px}
.related ul{columns:2 260px;padding-left:1.2em;margin:0}.related li{margin:2px 0}.related a{display:inline-block;padding:9px 0}
.cols-list{list-style:none;padding:0}.cols-list li{margin:0}.cols-list a{display:inline-flex;align-items:center;min-height:44px}
code{font-family:var(--mono);font-size:.92em}

/* footer */
.site-foot{background:#0d2536;color:#e4eef5;padding:20px 0 26px;margin-top:20px;font-size:.93rem}
.site-foot a{color:#bfdcf2}
.foot-brand{font-weight:700;margin:0 0 4px}
.foot-links{display:flex;flex-wrap:wrap;gap:0 14px}
.foot-links a{display:inline-flex;align-items:center;justify-content:center;min-width:44px;min-height:44px}
.site-foot p{margin:4px 0}

@media (prefers-reduced-motion:no-preference){.btn{transition:background-color .15s,border-color .15s}}

@media (max-width:400px){
 h1{font-size:1.5rem;margin:6px 0 4px}
 .intro{font-size:.92rem;line-height:1.38;margin:0 0 6px}
 .crumbs ol{margin:0}
 .tool{padding:6px}.panel{padding:8px}.tool-grid{gap:6px}
 .field{margin:0 0 6px}
 .field>label,.lbl{margin:0 0 2px;font-size:.88rem}
 input[type=text],select{padding:6px 8px}
 .results{padding:2px 8px}
 .row dt{font-size:.78rem}
 .v{font-size:.9rem}
 .btn.small{padding:2px 6px;font-size:.8rem}
}
/* stacked rows: label on its own line, value + Copy below; binary rows: Copy beside the label, value on its own line, sized to fit so it never wraps inside an octet */
@media (max-width:480px){
 .row{grid-template-columns:minmax(0,1fr) auto;gap:0 6px;padding-top:4px}
 .row dt{grid-column:1/-1}
 .row.bin{container-type:inline-size;grid-template-columns:minmax(0,1fr) auto}
 .row.bin dt{grid-column:1;grid-row:1}
 .row.bin .cp{grid-column:2;grid-row:1}
 .row.bin dd.v{grid-column:1/-1;grid-row:2;font-size:min(.8rem,4.5cqw);white-space:nowrap;padding-bottom:6px}
}
/* print: inputs and results only; the cheat sheet prints as one page */
@media print{
 @page{margin:.5in}
 body{background:#fff;color:#000;font-size:11pt}
 .site-head,.site-foot,.crumbs,.skip,.page-content,.actions-wrap,.btn,.handoff,.intro,.hint,.status,textarea,noscript,.last-updated,.ref-line,.cp{display:none!important}
 .splitbox{display:none!important}
 .tool,.panel,.results{background:#fff!important;border:1px solid #000!important;color:#000}
 .res-formula,.res-calc,.row dt{color:#000!important}
 .row{grid-template-columns:minmax(0,9.5rem) minmax(0,1fr)}
 input[type=text],select{border:1px solid #000;background:#fff;color:#000}
 a{color:#000;text-decoration:none}
 body[data-page=sheet] .tool{display:none!important}
 body[data-page=sheet]{font-size:9pt}
 body[data-page=sheet] h1{font-size:14pt;margin:2pt 0}
 .chart-sec h2{font-size:11pt;margin:4pt 0}
 .print-brand{display:block;margin:0;font-weight:700}
 .chart{max-height:none;overflow:visible;margin:2pt 0}
 .chart table{font-size:9pt;line-height:1.15}
 .chart th,.chart td{padding:1.5pt 6pt;background:#fff!important;color:#000}
 .chart thead th{position:static;box-shadow:none}
 .chart tr{break-inside:avoid}
}

/* batch C: IP range to CIDR and VLSM */
.tbl:has(> .rtable),.tbl:has(> .vtable){position:relative}
.rtable td,.rtable th,.vtable td,.vtable th{vertical-align:middle}
.rtable .v,.vtable .v{font-weight:700;overflow-wrap:normal;white-space:nowrap}
.rtable th[scope=row]{background:#fff}
.vtable th[scope=row]{background:#fff;font-weight:700}
.acts{white-space:nowrap}
.acts .btn{margin:2px 4px 2px 0}
.rtable .btn,.vtable .btn{text-decoration:none}
.total{margin:8px 0 0;font-weight:700;overflow-wrap:anywhere}
.free{margin:8px 0 0;font-weight:600;overflow-wrap:anywhere}
.vtable tr.nofit td,.vtable tr.skip td{color:var(--err);font-weight:600}
.vtable tr.skip td{color:var(--muted)}
.vlsm-rows{margin:6px 0 0}
.vhead,.vrow{display:grid;grid-template-columns:minmax(0,1fr) 6.5rem auto;gap:8px;align-items:center}
.vhead{font-weight:600;font-size:.88rem;margin:0 0 3px}
.vrow{margin:0 0 8px}
.vbtns{display:flex;flex-wrap:wrap;align-items:center;gap:8px 18px;margin-top:6px}
.chk{display:inline-flex;align-items:center;gap:8px;min-height:44px;font-weight:600}
.chk input{width:22px;height:22px;margin:0}
.vbar{display:block;width:100%;height:64px;margin:12px 0 0;background:#fff;border:2px solid #0d2536;border-radius:6px}
.vbar rect{stroke:#0d2536;stroke-width:1.5}
.vbar rect.free{fill:url(#vlsm-hatch)}
.vbar .s0{fill:#c7dff3}.vbar .s1{fill:#cfe9d6}.vbar .s2{fill:#f5e1b3}.vbar .s3{fill:#dcd0f0}.vbar .s4{fill:#f6cfc9}
.vbar text{fill:#0d2536;font:700 12px var(--sans)}
.vbar .seg-cidr{font:600 11px var(--mono)}
.vbar .free-label{stroke:#fff;stroke-width:4px;paint-order:stroke}
@media (max-width:400px){
 .vhead,.vrow{grid-template-columns:minmax(0,1fr) 4.6rem auto;gap:6px}
 .vrow .btn.small{padding:2px 6px;font-size:.78rem}
}
@media print{
 .acts,.vbtns,.vhead,.vrow .btn{display:none!important}
 .vrow{grid-template-columns:minmax(0,1fr) 6rem}
 .vbar{border-color:#000}
 .vtable tr.nofit td,.vtable tr.skip td{color:#000}
}