:root {
  --color-bg: #0b1020;
  --color-surface: #111827;
  --color-surface-muted: #172036;
  --color-border: #334155;

  --color-text-primary: #e5e7eb;
  --color-text-secondary: #cbd5e1;
  --color-text-muted: #94a3b8;

  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-success: #16a34a;
  --color-danger: #dc2626;
  --color-warning: #d97706;
  --color-timeout: #f59e0b;
  --color-learning: #38bdf8;

  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, monospace;

  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 40px;

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-pill: 999px;

  --shadow-soft: 0 10px 30px rgba(0, 0, 0, 0.18);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-body);
  background: var(--color-bg);
  color: var(--color-text-primary);
  line-height: 1.6;
}

a {
  color: #93c5fd;
  text-decoration: none;
}

a:hover { text-decoration: underline; }

a:focus-visible,
button:focus-visible,
textarea:focus-visible,
input:focus-visible,
select:focus-visible,
summary:focus-visible {
  outline: 2px solid #93c5fd;
  outline-offset: 2px;
}

.container {
  width: min(100%, 1040px);
  margin: 0 auto;
  padding: var(--space-6);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(11, 16, 32, 0.92);
  border-bottom: 1px solid rgba(51, 65, 85, 0.7);
  backdrop-filter: blur(8px);
}

.site-header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-4);
  padding-top: var(--space-4);
  padding-bottom: var(--space-4);
}

.brand {
  font-weight: 700;
  color: #fff;
}

.site-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: var(--space-3);
}

.site-nav a {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 0 12px;
  border-radius: var(--radius-pill);
  color: var(--color-text-secondary);
  background: rgba(15, 23, 42, 0.72);
  border: 1px solid rgba(51, 65, 85, 0.8);
  transition: background-color 120ms ease, color 120ms ease, border-color 120ms ease;
}

.site-nav a:hover {
  text-decoration: none;
  color: #fff;
  background: rgba(37, 99, 235, 0.18);
  border-color: rgba(96, 165, 250, 0.5);
}

h1, h2, h3 {
  color: #fff;
  line-height: 1.25;
}

h1 {
  font-size: 42px;
  margin: 0 0 var(--space-4);
}

h2 {
  font-size: 22px;
  margin-top: 0;
  margin-bottom: var(--space-2);
}

p, li {
  color: var(--color-text-secondary);
}

.eyebrow,
.dashboard-card__eyebrow {
  margin: 0 0 var(--space-3);
  color: var(--color-learning);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.hero-section {
  display: grid;
  grid-template-columns: 1.6fr 1fr;
  gap: var(--space-6);
  align-items: stretch;
  margin-top: var(--space-6);
}

.hero-copy,
.hero-panel__card,
.dashboard-card,
.info-card,
.playground,
.custom-test,
.results,
.problem-content,
.problem-card,
.filter-panel,
.home-section {
  background: var(--color-surface);
  border: 1px solid rgba(51, 65, 85, 0.85);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-soft);
}

.hero-copy {
  padding: 32px;
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.12), rgba(17, 24, 39, 1));
}

.hero-lead {
  font-size: 18px;
  color: #dbeafe;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-top: var(--space-5);
}

.button-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 16px;
  border-radius: 12px;
  font-weight: 700;
  text-decoration: none;
}

.button-link:hover { text-decoration: none; }

.button-link--primary {
  background: var(--color-primary);
  color: white;
}

.button-link--secondary {
  background: #1f2937;
  color: white;
}

.hero-panel__card {
  height: 100%;
  padding: 28px;
  background: linear-gradient(180deg, rgba(56, 189, 248, 0.12), rgba(17, 24, 39, 1));
}

.hero-panel__label {
  display: inline-block;
  margin-bottom: var(--space-3);
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  background: rgba(56, 189, 248, 0.16);
  color: #bae6fd;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.dashboard-grid,
.home-info-grid,
.quick-links {
  display: grid;
  gap: var(--space-4);
}

.dashboard-grid {
  grid-template-columns: repeat(3, 1fr);
  margin-top: var(--space-6);
}

.dashboard-card {
  padding: 24px;
}

.dashboard-card--today {
  background: linear-gradient(180deg, rgba(99, 102, 241, 0.08), rgba(17, 24, 39, 1));
}

.dashboard-card--algorithm {
  background: linear-gradient(180deg, rgba(34, 197, 94, 0.08), rgba(17, 24, 39, 1));
}

.dashboard-card--learning {
  background: linear-gradient(180deg, rgba(14, 165, 233, 0.10), rgba(17, 24, 39, 1));
}

.home-section {
  margin-top: var(--space-6);
  padding: 24px;
}

.home-info-grid {
  grid-template-columns: repeat(3, 1fr);
}

.info-card {
  padding: 20px;
}

.quick-links {
  grid-template-columns: repeat(3, 1fr);
}

.quick-link {
  display: block;
  padding: 18px 20px;
  border-radius: var(--radius-md);
  background: #0f172a;
  border: 1px solid rgba(51, 65, 85, 0.85);
  color: #e5e7eb;
  font-weight: 600;
}

.section-lead {
  margin: 0 0 var(--space-6);
  color: var(--color-text-muted);
}

.section-heading {
  margin-bottom: var(--space-4);
}

.section-heading p {
  margin: 0;
}

.meta-row,
.action-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-3) 0 var(--space-5);
}

.meta-row.compact,
.compact-row {
  margin: 0;
}

.pill,
.editor-badge {
  display: inline-block;
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  background: var(--color-surface-muted);
  color: var(--color-text-secondary);
  font-size: 14px;
}

.learning-card {
  margin-top: var(--space-5);
  padding: 18px;
  border-radius: var(--radius-md);
  border: 1px solid rgba(56, 189, 248, 0.35);
  background: linear-gradient(180deg, rgba(14, 165, 233, 0.08), rgba(2, 6, 23, 0.45));
}

.learning-card__title {
  margin: 0 0 var(--space-3);
  color: #e0f2fe;
  font-size: 18px;
}

.content-toggle {
  margin-top: var(--space-5);
  border: 1px solid rgba(51, 65, 85, 0.85);
  border-radius: var(--radius-md);
  background: #0f172a;
  overflow: hidden;
}

.content-toggle__summary {
  cursor: pointer;
  list-style: none;
  padding: 14px 16px;
  font-weight: 700;
  color: #fff;
}

.content-toggle__summary::-webkit-details-marker {
  display: none;
}

.content-toggle__summary::before {
  content: '▸';
  display: inline-block;
  margin-right: 8px;
  color: var(--color-text-muted);
  transition: transform 120ms ease;
}

.content-toggle[open] .content-toggle__summary::before {
  transform: rotate(90deg);
}

.content-toggle > :not(summary) {
  padding-left: 16px;
  padding-right: 16px;
}

.content-toggle > :last-child {
  padding-bottom: 16px;
}

.filter-panel {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--space-4);
  margin-top: var(--space-6);
  padding: 20px;
}

.filter-panel--wide {
  grid-template-columns: 2fr 1fr 1fr 1fr;
}

.filter-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.filter-label {
  font-size: 14px;
  color: var(--color-text-muted);
}

.filter-input,
.filter-select,
.custom-input {
  width: 100%;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--color-border);
  background: #020617;
  color: var(--color-text-primary);
  font: inherit;
}

.custom-input {
  min-height: 110px;
  resize: vertical;
  font-family: var(--font-mono);
}

.custom-test,
.results,
.problem-content,
.problem-card,
.playground,
.comments-section {
  margin-top: var(--space-6);
  padding: 20px;
}

.comments-section #disqus_thread {
  margin-top: var(--space-4);
}

.custom-test__panel {
  display: grid;
  gap: var(--space-3);
}

.custom-output {
  min-height: 56px;
  padding: var(--space-4);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: #020617;
  color: var(--color-text-secondary);
  font-family: var(--font-mono);
  white-space: pre-wrap;
  word-break: break-word;
}

#custom-run-btn {
  background: #0f766e;
  color: white;
}

.problem-count {
  margin: var(--space-4) 0 0;
}

.problem-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-4);
}

.problem-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.problem-card__title {
  margin: 0 0 var(--space-3);
  font-size: 20px;
}

.problem-card__title a {
  color: #fff;
}

.problem-card__description {
  margin: 0;
  color: var(--color-text-muted);
}

.problem-card__footer {
  margin-top: var(--space-5);
  padding-top: var(--space-4);
  border-top: 1px solid rgba(51, 65, 85, 0.55);
}

.text-link {
  font-weight: 600;
}

.editor-shell {
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: #020617;
}

.editor-shell__top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-3);
  padding: 10px 12px;
  border-bottom: 1px solid rgba(51, 65, 85, 0.85);
  background: #0f172a;
}

.editor-container {
  width: 100%;
  min-height: 360px;
}

.editor-fallback {
  width: 100%;
  min-height: 320px;
  padding: var(--space-4);
  border: 0;
  background: #020617;
  color: #e2e8f0;
  font-family: var(--font-mono);
  font-size: 14px;
  line-height: 1.5;
  resize: vertical;
}

.editor-fallback.is-hidden,
.editor-container.is-hidden,
.empty-state.is-hidden {
  display: none;
}

button {
  appearance: none;
  border: 0;
  border-radius: 10px;
  padding: 10px 14px;
  cursor: pointer;
  font-weight: 600;
  transition: transform 120ms ease, background-color 120ms ease, opacity 120ms ease;
}

button:hover { transform: translateY(-1px); }

#run-btn {
  background: var(--color-primary);
  color: white;
}

#run-btn:hover { background: var(--color-primary-hover); }

#reset-btn {
  background: #374151;
  color: white;
}

.results-list {
  display: grid;
  gap: var(--space-3);
}

.empty-state {
  padding: var(--space-4);
  border-radius: var(--radius-md);
  border: 1px dashed rgba(51, 65, 85, 0.85);
  background: rgba(2, 6, 23, 0.5);
  color: var(--color-text-muted);
}

.result-card {
  padding: var(--space-4);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: #020617;
}

.result-card.is-pass {
  border-color: rgba(22, 163, 74, 0.45);
}

.result-card.is-fail,
.result-card.is-error {
  border-color: rgba(220, 38, 38, 0.45);
}

.result-card.is-timeout {
  border-color: rgba(245, 158, 11, 0.55);
}

.result-card__status {
  font-weight: 700;
  margin-bottom: var(--space-3);
}

.result-line {
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: var(--space-3);
  align-items: start;
  margin-top: var(--space-2);
}

.result-line__label {
  color: var(--color-text-muted);
  font-size: 14px;
  text-transform: lowercase;
}

code,
.result-line__value {
  padding: 2px 6px;
  border-radius: 6px;
  background: var(--color-surface-muted);
  color: var(--color-text-primary);
  font-family: var(--font-mono);
  word-break: break-word;
}

.muted { color: var(--color-text-muted); }
.status-success { color: #86efac; }
.status-fail { color: #fca5a5; }
.status-warning { color: #fdba74; }
.status-timeout { color: #fbbf24; }

@media (max-width: 820px) {
  .hero-section,
  .dashboard-grid,
  .home-info-grid,
  .quick-links,
  .filter-panel,
  .filter-panel--wide {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .container {
    padding: var(--space-5);
  }

  .site-header .container {
    align-items: flex-start;
    flex-direction: column;
  }

  h1 { font-size: 32px; }

  .hero-copy,
  .hero-panel__card,
  .dashboard-card,
  .home-section,
  .info-card,
  .playground,
  .custom-test,
  .results,
  .problem-content,
  .problem-card,
  .filter-panel {
    padding: 20px;
  }

  .editor-container {
    min-height: 280px;
  }

  .editor-fallback {
    min-height: 260px;
  }

  .editor-shell__top {
    align-items: flex-start;
    flex-direction: column;
  }

  .result-line {
    grid-template-columns: 1fr;
    gap: var(--space-1);
  }
}