/* Base styles */
:root {
  --bg: #f4f7fb;
  --bg-alt: #edf2f9;
  --surface: #ffffff;
  --surface-strong: #f8fbff;
  --text: #163042;
  --text-soft: #4f6474;
  --line: #d8e2ee;
  --accent: #1464b4;
  --accent-soft: #dceeff;
  --success: #18794e;
  --warn: #a15c00;
  --danger: #b42318;
  --shadow: 0 14px 40px rgba(17, 42, 71, 0.08);
  --radius: 18px;
  --radius-sm: 12px;
  --code: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(20, 100, 180, 0.08), transparent 34%),
    radial-gradient(circle at top right, rgba(20, 100, 180, 0.06), transparent 26%),
    var(--bg);
  line-height: 1.6;
}

img {
  max-width: 100%;
}

a {
  color: inherit;
}

.container {
  width: min(1120px, calc(100% - 2rem));
  margin: 0 auto;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
  background: var(--surface);
  padding: 0.75rem 1rem;
  border-radius: 999px;
  box-shadow: var(--shadow);
  z-index: 1000;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  background: rgba(244, 247, 251, 0.86);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(216, 226, 238, 0.8);
}

.nav-wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 76px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand strong {
  display: block;
  font-size: 1rem;
  letter-spacing: 0.02em;
}

.brand span {
  display: block;
  font-size: 0.86rem;
  color: var(--text-soft);
}

.brand-mark {
  display: inline-grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--accent), #0c8e84);
  color: white;
  font-weight: 800;
  font-size: 1.15rem;
}

.site-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 0.85rem 1rem;
}

.site-nav a {
  text-decoration: none;
  color: var(--text-soft);
  font-weight: 600;
  font-size: 0.96rem;
}

.site-nav a:hover,
.site-nav a:focus {
  color: var(--accent);
}

.hero {
  padding: 4.5rem 0 3rem;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1.5rem;
  align-items: stretch;
}

.eyebrow {
  display: inline-block;
  margin: 0 0 0.65rem;
  font-size: 0.85rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 800;
}

h1,
h2,
h3 {
  line-height: 1.15;
  margin-top: 0;
}

h1 {
  margin-bottom: 1rem;
  font-size: clamp(2.5rem, 5vw, 4rem);
}

h2 {
  margin-bottom: 0.75rem;
  font-size: clamp(1.8rem, 3vw, 2.5rem);
}

h3 {
  margin-bottom: 0.75rem;
  font-size: 1.2rem;
}

.hero-copy,
.section-copy,
.tool-copy,
.panel-copy {
  color: var(--text-soft);
}

.hero-actions,
.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.2rem 0 1.1rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-height: 46px;
  padding: 0.75rem 1.15rem;
  border-radius: 999px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: white;
  text-decoration: none;
  font-weight: 700;
  cursor: pointer;
  transition: transform 140ms ease, box-shadow 140ms ease, opacity 140ms ease;
  box-shadow: 0 10px 22px rgba(20, 100, 180, 0.2);
}

.btn:hover,
.btn:focus {
  transform: translateY(-1px);
}

.btn.ghost {
  background: transparent;
  color: var(--accent);
  box-shadow: none;
}

.btn.small {
  min-height: 40px;
  padding: 0.65rem 1rem;
  font-size: 0.95rem;
}

.hero-points,
.check-list,
.steps {
  margin: 0;
  padding-left: 1.15rem;
}

.hero-points li,
.check-list li,
.steps li {
  margin-bottom: 0.5rem;
}

.hero-panel,
.info-card,
.panel,
.tool-card,
.result-box,
.vocab-card,
.quiz-question {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-panel {
  padding: 1.35rem;
}

.mini-rows {
  display: grid;
  gap: 0.85rem;
}

.mini-row {
  display: grid;
  grid-template-columns: 90px 1fr;
  gap: 0.75rem;
  align-items: start;
  padding: 0.9rem;
  border-radius: var(--radius-sm);
  background: var(--surface-strong);
}

.mini-row p {
  margin: 0;
}

.mini-label {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 32px;
  padding: 0.2rem 0.55rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 800;
  font-size: 0.85rem;
}

.section {
  padding: 2rem 0 2.75rem;
}

.section.alt {
  background: linear-gradient(180deg, rgba(237, 242, 249, 0.55), rgba(237, 242, 249, 0.15));
}

.section-head {
  margin-bottom: 1.3rem;
}

.section-head.split {
  display: flex;
  justify-content: space-between;
  align-items: end;
  gap: 1rem;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin-bottom: 1rem;
}

.info-card {
  padding: 1.15rem;
}

.two-col {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.panel {
  padding: 1.2rem;
}

.search-wrap {
  max-width: 360px;
  width: 100%;
}

input,
select,
button,
textarea {
  font: inherit;
}

label {
  display: block;
  margin-bottom: 0.35rem;
  font-weight: 700;
  color: var(--text);
}

input,
select,
textarea {
  width: 100%;
  min-height: 46px;
  padding: 0.8rem 0.95rem;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  color: var(--text);
}

input:focus,
select:focus,
textarea:focus,
button:focus {
  outline: 3px solid rgba(20, 100, 180, 0.18);
  outline-offset: 2px;
}

.sr-only {
  position: absolute;
  left: -9999px;
}

.vocab-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
}

.vocab-card {
  padding: 1rem;
}

.vocab-card h3 {
  margin-bottom: 0.45rem;
}

.vocab-card p {
  margin: 0.2rem 0 0;
}

.vocab-example {
  margin-top: 0.6rem;
  padding-top: 0.65rem;
  border-top: 1px dashed var(--line);
  color: var(--text-soft);
  font-size: 0.95rem;
}

.accordion-stack {
  display: grid;
  gap: 0.8rem;
}

details {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}

summary {
  padding: 1rem 1.15rem;
  cursor: pointer;
  font-weight: 800;
  list-style: none;
}

summary::-webkit-details-marker {
  display: none;
}

.detail-body {
  padding: 0 1.15rem 1.1rem;
  color: var(--text-soft);
}

.tool-stack {
  display: grid;
  gap: 1rem;
}

.tool-card {
  padding: 1.2rem;
}

.tool-title-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
}

.tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 30px;
  padding: 0.2rem 0.65rem;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 999px;
  font-weight: 800;
  font-size: 0.84rem;
}

.form-grid {
  display: grid;
  gap: 0.85rem;
}

.form-grid.one {
  grid-template-columns: 1fr;
}

.form-grid.two {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.form-grid.three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.form-grid.four {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.result-box {
  margin-top: 0.9rem;
  padding: 1rem;
  background: var(--surface-strong);
  min-height: 66px;
}

.result-box:empty {
  display: none;
}

.result-box.error {
  border-color: rgba(180, 35, 24, 0.25);
  background: rgba(180, 35, 24, 0.06);
}

.result-box.success {
  border-color: rgba(24, 121, 78, 0.22);
  background: rgba(24, 121, 78, 0.07);
}

.result-box.info {
  border-color: rgba(20, 100, 180, 0.2);
  background: rgba(20, 100, 180, 0.05);
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.7rem;
}

.result-item {
  padding: 0.85rem;
  border-radius: 14px;
  background: white;
  border: 1px solid var(--line);
}

.result-item .label {
  display: block;
  margin-bottom: 0.2rem;
  font-size: 0.82rem;
  color: var(--text-soft);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.result-item .value {
  font-family: var(--code);
  font-size: 1rem;
  word-break: break-word;
}

.subtle {
  margin-top: 0.8rem;
  color: var(--text-soft);
  font-size: 0.95rem;
}

.mono {
  font-family: var(--code);
}

.table-wrap {
  overflow-x: auto;
}

table {
  width: 100%;
  border-collapse: collapse;
  min-width: 720px;
}

th,
td {
  text-align: left;
  padding: 0.8rem 0.9rem;
  border-bottom: 1px solid var(--line);
}

thead th {
  background: rgba(20, 100, 180, 0.06);
  color: var(--text);
}

tbody tr:nth-child(even) {
  background: rgba(248, 251, 255, 0.75);
}

.practice-box {
  font-weight: 700;
}

.quiz-form {
  display: grid;
  gap: 0.9rem;
}

.quiz-question {
  padding: 1rem;
}

.quiz-question p {
  margin-top: 0;
  font-weight: 800;
}

.quiz-options {
  display: grid;
  gap: 0.5rem;
}

.quiz-options label {
  display: flex;
  align-items: start;
  gap: 0.55rem;
  font-weight: 500;
  padding: 0.55rem 0.7rem;
  border-radius: 12px;
  background: var(--surface-strong);
  border: 1px solid var(--line);
}

.quiz-options input {
  width: auto;
  min-height: auto;
  margin-top: 0.25rem;
  padding: 0;
}

.bit-visual {
  display: grid;
  gap: 0.75rem;
}

.bit-row {
  display: grid;
  gap: 0.25rem;
}

.bit-label {
  font-weight: 800;
}

.bit-groups {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  align-items: center;
}

.bit-group {
  display: inline-flex;
  gap: 0.18rem;
  padding: 0.35rem 0.4rem;
  border-radius: 10px;
  background: white;
  border: 1px solid var(--line);
}

.bit {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.6rem;
  height: 1.9rem;
  border-radius: 10px;
  font-family: var(--code);
  font-size: 0.92rem;
  font-weight: 700;
}

.bit.net {
  background: rgba(20, 100, 180, 0.12);
  color: var(--accent);
}

.bit.host {
  background: rgba(12, 142, 132, 0.12);
  color: #0b776f;
}

.bit.note {
  width: auto;
  padding: 0 0.5rem;
  background: transparent;
  color: var(--text-soft);
}

.badge-line {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 0.85rem;
}

.badge {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  padding: 0.2rem 0.65rem;
  border-radius: 999px;
  background: white;
  border: 1px solid var(--line);
  color: var(--text);
  font-weight: 700;
  font-size: 0.9rem;
}

.site-footer {
  padding: 2rem 0 3rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  color: var(--text-soft);
}

code {
  font-family: var(--code);
  padding: 0.1rem 0.35rem;
  background: rgba(20, 100, 180, 0.08);
  border-radius: 0.4rem;
}

@media (max-width: 960px) {
  .hero-grid,
  .two-col,
  .card-grid,
  .vocab-grid,
  .footer-grid,
  .form-grid.two,
  .form-grid.three,
  .form-grid.four {
    grid-template-columns: 1fr;
  }

  .section-head.split,
  .nav-wrap {
    flex-direction: column;
    align-items: stretch;
  }

  .site-nav {
    justify-content: flex-start;
  }

  .mini-row {
    grid-template-columns: 1fr;
  }

  .result-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .hero {
    padding-top: 3rem;
  }

  .container {
    width: min(100% - 1rem, 1120px);
  }

  .btn,
  input,
  select {
    width: 100%;
  }

  .button-row {
    flex-direction: column;
  }
}