:root {
  --bg-primary: #000;
  --bg-secondary: #0a0a0a;
  --bg-tertiary: #141414;
  --text-primary: #ffffff;
  --text-secondary: #a0a0a0;
  --accent: #00ff88;
  --accent-dim: #00cc6a;
  --border: #2a2a2a;
  --radius: 18px;
}

* {
  box-sizing: border-box;
}

body {
  font-family: 'Roboto Mono', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.bg-grid {
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(0, 255, 136, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 255, 136, 0.06) 1px, transparent 1px);
  background-size: 50px 50px;
  animation: grid-move 20s linear infinite;
  z-index: 0;
}

@keyframes grid-move {
  0% { transform: translate(0, 0); }
  100% { transform: translate(50px, 50px); }
}

.site-nav {
  position: sticky;
  top: 0;
  width: 100%;
  background: rgba(0, 0, 0, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  z-index: 10;
}

.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 22px 5%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--accent);
  text-decoration: none;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.brand-logo {
  height: 48px;
  width: auto;
  display: block;
}

.nav-title {
  color: var(--text-secondary);
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.main-container {
  max-width: 1100px;
  width: 100%;
  margin: 0 auto;
  padding: 120px 5% 80px;
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  gap: 28px;
  flex: 1 0 auto;
}

.card {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: 0 24px 48px rgba(0, 0, 0, 0.35);
}

.main-container .card + .card {
  margin-top: 12px;
}

h1 {
  margin: 0 0 18px;
  font-size: clamp(32px, 4vw, 46px);
  font-weight: 700;
}

h2 {
  margin: 0 0 12px;
  color: var(--accent);
  font-size: clamp(22px, 3vw, 28px);
}

label > span {
  display: block;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.card form > * + * {
  margin-top: 16px;
}
input[type="number"],
select {
  width: 100%;
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--bg-secondary);
  color: var(--text-primary);
}

input:focus,
select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(0, 255, 136, 0.18);
}

.grid {
  display: grid;
  gap: 24px;
  grid-template-columns: 1fr;
}

@media (min-width: 780px) {
  .grid { grid-template-columns: 1fr 1fr; }
}

fieldset {
  border: none;
  padding: 0;
  margin: 18px 0 12px;
}

.actions {
  margin-top: 26px;
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}

.check {
  display: inline-flex;
  gap: 8px;
  align-items: center;
  color: var(--text-secondary);
}

button {
  background: var(--accent);
  color: #001b10;
  border: none;
  border-radius: 999px;
  padding: 12px 24px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

button:hover:not([disabled]) {
  transform: translateY(-1px);
  box-shadow: 0 14px 28px rgba(0, 255, 136, 0.25);
}

button[disabled] {
  opacity: 0.55;
  cursor: not-allowed;
  box-shadow: none;
  transform: none;
}

button.secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}

.next-btn {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}

.list {
  list-style: none;
  padding-left: 0;
  margin: 0;
}

.list li {
  padding: 6px 0;
  color: var(--text-secondary);
}

.alert {
  background: rgba(0, 255, 136, 0.12);
  border: 1px solid var(--accent-dim);
  color: var(--accent);
  padding: 12px 16px;
  border-radius: 14px;
  margin-bottom: 18px;
}

.quiz-header {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.qh-left { display: flex; flex-direction: column; gap: 6px; }
.meta-top { font-size: 0.95rem; color: var(--text-secondary); font-style: italic; font-weight: 700; }
.unit-title { font-size: 1.2rem; margin: 0; }

.progress-wrap { margin-top: 6px; }
.progress-top { font-size: 0.85rem; color: var(--text-secondary); }

.progress-bar {
  width: 260px;
  max-width: 60vw;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 999px;
  overflow: hidden;
}

#progress-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width 0.35s ease;
}

.qh-right { display: flex; align-items: center; gap: 10px; }

.timer {
  background: rgba(0, 255, 136, 0.12);
  border: 1px solid var(--accent-dim);
  border-radius: 12px;
  padding: 6px 12px;
  color: var(--accent);
  font-weight: 600;
}

.quiz .prompt {
  font-size: 1.05rem;
  margin: 10px 0 16px;
}

.choices {
  display: grid;
  gap: 12px;
}

.choice {
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 12px 16px;
  cursor: pointer;
  background: var(--bg-secondary);
  color: var(--text-primary);
  text-align: left;
  transition: border-color 0.2s ease, transform 0.1s ease;
}

.choice:hover {
  border-color: var(--accent);
  transform: translateY(-1px);
}

.choice.correct {
  border-color: var(--accent);
  background: rgba(0, 255, 136, 0.12);
}

.choice.incorrect {
  border-color: #ff5c5c;
  background: rgba(255, 92, 92, 0.12);
}

.yn {
  display: flex;
  gap: 10px;
}

.results {
  line-height: 1.32;
}

.results .score {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 10px;
}

.results .result-item {
  padding: 12px 14px;
  font-size: 0.9rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--bg-secondary);
  margin-top: 10px;
}

.results .answer-line { margin-top: 4px; color: var(--text-secondary); }
.results .explanation { margin-top: 6px; font-size: 0.86rem; color: var(--text-secondary); }

.results button {
  margin-top: 10px;
}

.card.help {
  font-size: 0.9rem;
}

.card.help h2 {
  font-size: 1.05rem;
  margin-bottom: 8px;
}

.card.help ul {
  margin: 6px 0 0 18px;
  padding: 0;
}

.card.help li {
  margin: 4px 0;
}

.site-footer {
  border-top: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.82);
  flex-shrink: 0;
}

.footer-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 30px 5%;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.footer-container a {
  color: var(--text-secondary);
  text-decoration: underline;
}

@media (max-width: 700px) {
  .main-container { padding-top: 110px; }
  .quiz-header { flex-direction: column; align-items: flex-start; }
  .progress-bar { width: 100%; max-width: 100%; }
}