:root {
  color-scheme: dark;
  --ink: #edf5f0;
  --muted: #9caaa3;
  --paper: #0d1512;
  --card: rgba(20,31,27,.92);
  --surface: #16231e;
  --surface-soft: #111c18;
  --input: #111c18;
  --line: #2d3d36;
  --line-soft: #25342e;
  --green: #b8ef62;
  --green-dark: #a8e75b;
  --orange: #ff9874;
  --danger-bg: #38201c;
  --danger: #ff9c82;
  --shadow: rgba(0,0,0,.3);
  --grid: rgba(237,245,240,.035);
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  --sans: Inter, "Segoe UI", Arial, sans-serif;
}
[data-theme="light"] {
  color-scheme: light;
  --ink: #16241f; --muted: #64716c; --paper: #f4f5ef;
  --card: rgba(255,255,252,.92); --surface: #fbfcf8; --surface-soft: #fbfcf8;
  --input: #fafbf7; --line: #d9ded6; --line-soft: #e7eae4;
  --green-dark: #1e4d38; --orange: #ef8059;
  --danger-bg: #fff0ec; --danger: #a63f25;
  --shadow: rgba(23,42,34,.07); --grid: rgba(22,36,31,.035);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--sans);
  -webkit-font-smoothing: antialiased;
}
.backdrop {
  position: fixed; inset: 0; pointer-events: none; z-index: -1;
  background:
    radial-gradient(circle at 85% 8%, rgba(184,239,98,.25), transparent 24rem),
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: auto, 32px 32px, 32px 32px;
}
.topbar, main, footer { width: min(1120px, calc(100% - 40px)); margin-inline: auto; }
.topbar {
  height: 80px; display: flex; align-items: center; justify-content: space-between;
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; gap: 11px; align-items: center; color: var(--ink); text-decoration: none; font-weight: 800; font-size: 20px; }
.brand-mark { display: grid; place-items: center; width: 36px; height: 36px; border-radius: 10px; background: var(--ink); color: var(--green); font: 500 13px var(--mono); }
.status { font: 500 12px var(--mono); text-transform: uppercase; letter-spacing: .08em; color: var(--muted); }
.status i { display: inline-block; width: 7px; height: 7px; margin-right: 7px; border-radius: 50%; background: #63bd55; box-shadow: 0 0 0 4px rgba(99,189,85,.12); }
.topbar-actions { display: flex; align-items: center; gap: 18px; }
.theme-toggle { display: flex; align-items: center; gap: 7px; min-height: 36px; padding: 0 11px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); color: var(--ink); font: 600 12px var(--sans); cursor: pointer; transition: border-color .2s, transform .2s; }
.theme-toggle:hover { border-color: var(--green-dark); transform: translateY(-1px); }
.theme-icon { color: var(--green-dark); font-size: 16px; line-height: 1; }
.hero { padding: 76px 0 48px; }
.eyebrow, .section-label { margin: 0 0 13px; color: var(--green-dark); font: 500 12px var(--mono); letter-spacing: .14em; }
h1 { max-width: 850px; margin: 0; font-size: clamp(48px, 7vw, 86px); line-height: .98; letter-spacing: -.065em; }
h1 span { color: var(--green-dark); }
.intro { max-width: 590px; margin: 30px 0 0; color: var(--muted); font-size: 17px; line-height: 1.7; }
.calculator, .results {
  border: 1px solid var(--line); border-radius: 22px; padding: 30px;
  background: var(--card); box-shadow: 0 20px 70px var(--shadow); backdrop-filter: blur(10px);
}
.panel-heading, .result-heading, .subnet-heading { display: flex; justify-content: space-between; align-items: end; gap: 20px; }
h2 { margin: 0; font-size: 24px; letter-spacing: -.03em; }
.text-button, .copy-button { padding: 0; border: 0; background: none; color: var(--green-dark); font: 600 13px var(--sans); cursor: pointer; border-bottom: 1px solid; }
.fields { display: grid; grid-template-columns: 1.45fr .8fr 1fr auto; gap: 14px; align-items: end; margin-top: 28px; }
label > span { display: block; margin: 0 0 8px 3px; font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; }
label small { color: var(--muted); font-weight: 500; }
input {
  width: 100%; height: 52px; border: 1px solid var(--line); border-radius: 12px; background: var(--input);
  padding: 0 15px; color: var(--ink); outline: none; font: 500 16px var(--mono); transition: .2s;
}
input:focus { border-color: var(--green-dark); box-shadow: 0 0 0 3px rgba(184,239,98,.12); background: var(--surface); }
.prefix-field { display: flex; align-items: center; position: relative; }
.prefix-field > span { position: absolute; z-index: 1; left: 15px; font: 500 16px var(--mono); color: var(--muted); }
.prefix-field input { padding-left: 29px; }
.prefix-field.muted > span { color: #9aa39f; }
.primary-button {
  height: 52px; padding: 0 22px; border: 0; border-radius: 12px; background: var(--green); color: #142019;
  font: 700 14px var(--sans); cursor: pointer; white-space: nowrap; transition: transform .2s, background .2s;
}
.primary-button:hover { background: #c7f77d; transform: translateY(-1px); }
.primary-button span { color: #1e4d38; font-size: 20px; margin-left: 12px; }
.hint, .error { margin: 13px 0 0; color: var(--muted); font-size: 12px; }
.error { padding: 10px 13px; border-radius: 8px; background: var(--danger-bg); color: var(--danger); }
.results { margin-top: 24px; animation: rise .45s ease both; }
@keyframes rise { from { opacity: 0; transform: translateY(10px); } }
.result-heading h2 { font: 500 26px var(--mono); }
.copy-button { border: 1px solid var(--line); border-radius: 9px; padding: 9px 12px; color: var(--ink); }
.summary-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 28px; overflow: hidden; border: 1px solid var(--line); border-radius: 14px; background: var(--line); }
.summary-grid article { min-width: 0; padding: 20px; background: var(--surface-soft); }
.summary-grid span { display: block; margin-bottom: 8px; color: var(--muted); font-size: 12px; }
.summary-grid strong { overflow-wrap: anywhere; font: 500 clamp(15px, 2vw, 19px) var(--mono); }
.details-grid { display: grid; grid-template-columns: .8fr 1.2fr; gap: 16px; margin-top: 16px; }
.detail-card, .subnet-card { border: 1px solid var(--line); border-radius: 14px; padding: 22px; background: var(--surface-soft); }
h3 { margin: 0; font-size: 16px; }
dl { margin: 17px 0 0; }
dl div { display: flex; justify-content: space-between; gap: 15px; padding: 10px 0; border-bottom: 1px solid var(--line-soft); }
dl div:last-child { border: 0; }
dt { color: var(--muted); font-size: 12px; }
dd { margin: 0; font: 500 12px var(--mono); text-align: right; }
.binary-card { min-width: 0; overflow: hidden; }
.legend { float: right; margin: -17px 0 0; color: var(--muted); font-size: 10px; }
.legend i { display: inline-block; width: 8px; height: 8px; margin: 0 4px 0 9px; border-radius: 2px; background: var(--green-dark); }
.legend i:nth-child(2) { background: var(--orange); }
.binary-row { display: grid; grid-template-columns: 72px 1fr; gap: 10px; margin-top: 16px; align-items: center; }
.binary-row > span { color: var(--muted); font-size: 11px; }
.bits { overflow-x: auto; white-space: nowrap; font: 500 12px/1.8 var(--mono); letter-spacing: .07em; }
.bits .network { color: var(--green-dark); background: rgba(184,239,98,.32); }
.bits .host { color: #a94729; background: rgba(239,128,89,.13); }
.bits b { padding: 4px 1px; font-weight: 500; }
.bits em { display: inline-block; width: 7px; }
.subnet-card { margin-top: 16px; }
.subnet-heading { align-items: center; }
.subnet-heading h3 { font-size: 19px; }
.count-pill { padding: 7px 10px; border-radius: 99px; background: rgba(184,239,98,.32); color: var(--green-dark); font: 500 11px var(--mono); }
.table-wrap { overflow-x: auto; margin-top: 20px; }
table { width: 100%; border-collapse: collapse; white-space: nowrap; }
th, td { padding: 12px 15px; border-bottom: 1px solid var(--line-soft); text-align: left; font: 400 12px var(--mono); }
th { color: var(--muted); font: 700 10px var(--sans); letter-spacing: .06em; text-transform: uppercase; }
tbody tr:hover { background: rgba(184,239,98,.1); }
.table-note { margin: 13px 0 0; color: var(--muted); font-size: 11px; }
footer { display: flex; justify-content: space-between; padding: 38px 0; color: var(--muted); font: 500 11px var(--mono); }
@media (max-width: 850px) {
  .fields { grid-template-columns: 1fr 1fr; }
  .primary-button { width: 100%; }
  .summary-grid { grid-template-columns: 1fr 1fr; }
  .details-grid { grid-template-columns: 1fr; }
}
@media (max-width: 560px) {
  .topbar, main, footer { width: min(100% - 24px, 1120px); }
  .hero { padding: 52px 4px 36px; }
  h1 { font-size: 48px; }
  .calculator, .results { padding: 20px; border-radius: 16px; }
  .fields, .summary-grid { grid-template-columns: 1fr; }
  .panel-heading { align-items: center; }
  .result-heading { align-items: start; flex-direction: column; }
  .legend { float: none; margin: 8px 0 0; }
  .binary-row { grid-template-columns: 58px 1fr; }
  .status { display: none; }
}