/* Quality Engineering Guide shared styles */
:root {
  --bg: #080b1a;
  --fg: #d8e0f0;
  --muted: #8090b8;
  --accent: #7bd88f;
  --accent-2: #60a5fa;
  --card: #0d1028;
  --border: #1a2045;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
@media (max-width: 768px) { html { scroll-padding-top: 120px; } }
@media (max-width: 600px) { html { scroll-padding-top: 140px; } }
body { margin: 0; padding: 0; background: var(--bg); color: var(--fg); font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji"; }
a { color: inherit; text-decoration: none; }
a[href]:not(.btn):not(.brand a):not(.qe-card):not(.lesson-link):not(.quiz-option) { text-decoration: underline; text-decoration-color: rgba(123,216,143,0.5); text-underline-offset: 2px; }
a[href]:not(.btn):not(.brand a):not(.qe-card):not(.lesson-link):not(.quiz-option):hover { text-decoration-color: var(--accent); }
.container { max-width: 1120px; margin: 0 auto; padding: 24px; }

/* Header */
header { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding: 8px 0; border-bottom: 1px solid var(--border); position: sticky; top: 0; background: rgba(8,11,26,0.95); z-index: 10; }
header .container { display: flex; align-items: center; justify-content: space-between; gap: 12px; width: 100%; max-width: 1120px; }
.brand { display: flex; align-items: center; gap: 12px; font-weight: 700; letter-spacing: 0.2px; }
.brand a { color: var(--fg); text-decoration: none; }
.logo-emoji { font-size: 24px; line-height: 1; }
#main-nav { display: flex; gap: 16px; font-size: 14px; flex-wrap: wrap; }
#main-nav a.active { color: var(--accent); font-weight: 600; text-decoration: underline; text-decoration-color: var(--accent); }

/* Footer */
footer { margin-top: 48px; padding: 24px 0 48px; color: var(--muted); border-top: 1px solid var(--border); text-align: center; }
.footer-links { margin-top: 6px; }
.footer-text { margin-top: 6px; font-size: 13px; }
.social-links { margin-top: 24px; display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }
.social-links a { display: flex; align-items: center; justify-content: center; width: 40px; height: 40px; border-radius: 50%; background: var(--card); border: 1px solid var(--border); color: var(--muted); font-size: 18px; transition: all 0.2s ease; }
.social-links a:hover { background: var(--accent); color: #0d1117; transform: translateY(-3px); box-shadow: 0 4px 12px rgba(123,216,143,0.3); text-decoration: none; border-color: var(--accent); }
.social-links a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* Section layout */
.section-padding { padding-top: 32px; padding-bottom: 32px; }
.section-title { margin: 0 0 16px; font-size: clamp(28px, 5vw, 48px); line-height: 1.08; }
.section-intro { color: var(--muted); font-size: clamp(14px, 2.2vw, 18px); margin: 0 0 32px; line-height: 1.6; }

/* Breadcrumb */
.breadcrumb { font-size: 14px; color: var(--muted); margin-bottom: 24px; }
.breadcrumb a { color: var(--accent); }
.breadcrumb .sep { margin: 0 8px; }

/* Back link */
.back-link { display: inline-block; margin-bottom: 24px; color: var(--accent); font-size: 14px; font-weight: 600; }

/* Hub page card grid */
.qe-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(320px, 100%), 1fr)); gap: 24px; margin-top: 32px; }
.qe-card { display: block; background: var(--card); border: 1px solid var(--border); border-radius: 14px; padding: 28px; transition: transform 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease; text-decoration: none; }
.qe-card:hover { transform: translateY(-4px); border-color: var(--accent); box-shadow: 0 8px 24px rgba(123,216,143,0.15); }
.qe-card:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.qe-card .card-icon { font-size: 32px; margin-bottom: 16px; color: var(--accent); }
.qe-card h2 { font-size: 22px; margin: 0 0 12px; color: var(--fg); }
.qe-card p { font-size: 15px; color: var(--muted); margin: 0 0 16px; }
.card-meta { font-size: 13px; color: var(--muted); display: flex; align-items: center; gap: 6px; }

/* Topic index: lesson list */
.lesson-list { list-style: none; padding: 0; margin: 24px 0; counter-reset: lesson; }
.lesson-item { counter-increment: lesson; margin-bottom: 12px; }
.lesson-link { display: flex; align-items: center; gap: 16px; background: var(--card); border: 1px solid var(--border); border-radius: 12px; padding: 20px 24px; transition: border-color 0.2s ease, transform 0.1s ease; text-decoration: none; }
.lesson-link:hover { border-color: var(--accent); transform: translateX(4px); }
.lesson-link:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.lesson-number { display: flex; align-items: center; justify-content: center; min-width: 36px; height: 36px; border-radius: 50%; background: rgba(123,216,143,0.1); color: var(--accent); font-weight: 700; font-size: 14px; flex-shrink: 0; }
.lesson-info { flex: 1; }
.lesson-title { font-size: 16px; color: var(--fg); font-weight: 600; }
.lesson-desc { font-size: 14px; color: var(--muted); margin-top: 4px; }
.quiz-card { display: flex; align-items: center; gap: 16px; background: rgba(123,216,143,0.05); border: 2px solid var(--accent); border-radius: 12px; padding: 20px 24px; margin-top: 24px; transition: background 0.2s ease; text-decoration: none; }
.quiz-card:hover { background: rgba(123,216,143,0.1); }
.quiz-card .card-icon { font-size: 24px; color: var(--accent); flex-shrink: 0; }
.quiz-card .lesson-title { color: var(--accent); }

/* Content page */
.qe-content { max-width: 800px; }
.qe-content h1 { font-size: clamp(28px, 5vw, 42px); margin: 0 0 16px; line-height: 1.15; }
.qe-content h2 { font-size: 24px; margin: 32px 0 12px; color: var(--accent); }
.qe-content h3 { font-size: 18px; margin: 24px 0 8px; color: var(--accent-2); }
.qe-content p { line-height: 1.7; color: var(--muted); margin: 0 0 16px; }
.qe-content ul, .qe-content ol { color: var(--fg); padding-left: 24px; line-height: 1.7; }
.qe-content li { margin-bottom: 8px; }
.qe-content strong { color: var(--fg); }
.qe-content code { background: var(--card); border: 1px solid var(--border); border-radius: 4px; padding: 2px 6px; font-size: 13px; color: var(--accent); }
.qe-content pre { background: var(--card); border: 1px solid var(--border); border-radius: 8px; padding: 16px; overflow-x: auto; margin: 16px 0; }
.qe-content pre code { background: none; border: none; padding: 0; color: var(--fg); }

/* Resources box */
.resources-box { background: rgba(96,165,250,0.08); border: 1px solid rgba(96,165,250,0.2); border-radius: 12px; padding: 20px 24px; margin: 32px 0; }
.resources-box h3 { margin: 0 0 12px; color: var(--accent-2); font-size: 16px; }
.resources-box ul { margin: 0; padding-left: 20px; }
.resources-box li { margin-bottom: 6px; color: var(--muted); }
.resources-box a { color: var(--accent-2); }

/* Tip and warning boxes */
.tip-box { background: rgba(123,216,143,0.08); border-left: 4px solid var(--accent); padding: 16px 20px; border-radius: 0 8px 8px 0; margin: 20px 0; color: var(--muted); }
.tip-box strong { color: var(--accent); }
.warning-box { background: rgba(251,191,36,0.08); border-left: 4px solid #fbbf24; padding: 16px 20px; border-radius: 0 8px 8px 0; margin: 20px 0; color: var(--muted); }
.warning-box strong { color: #fbbf24; }

/* Lesson navigation (prev/next) */
.lesson-nav { display: flex; justify-content: space-between; margin-top: 40px; padding-top: 24px; border-top: 1px solid var(--border); gap: 16px; flex-wrap: wrap; }
.lesson-nav a { display: flex; align-items: center; gap: 8px; padding: 12px 20px; border: 1px solid var(--border); border-radius: 8px; font-weight: 600; font-size: 14px; color: var(--accent); transition: all 0.2s ease; }
.lesson-nav a:hover { border-color: var(--accent); background: rgba(123,216,143,0.08); }
.lesson-nav a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* CTA link */
.cta-link { display: inline-block; margin-top: 12px; padding: 8px 20px; border-radius: 8px; border: 1px solid var(--accent); color: var(--accent); font-weight: 600; font-size: 14px; transition: all 0.2s ease; }
.cta-link:hover { background: var(--accent); color: #0d1117; text-decoration: none; }
.cta-link:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* Quiz styles */
.quiz-container { max-width: 800px; }
.quiz-intro { color: var(--muted); font-size: 16px; margin-bottom: 32px; }
.quiz-question { background: var(--card); border: 1px solid var(--border); border-radius: 12px; padding: 24px; margin-bottom: 24px; }
.quiz-question h3 { margin: 0 0 16px; color: var(--fg); font-size: 18px; }
.quiz-question .q-num { color: var(--accent); font-weight: 600; }
.quiz-options { list-style: none; padding: 0; margin: 0; }
.quiz-option { padding: 12px 16px; margin-bottom: 8px; border: 1px solid var(--border); border-radius: 8px; cursor: pointer; transition: all 0.2s ease; color: var(--muted); font-size: 15px; }
.quiz-option:hover:not(.disabled) { border-color: var(--accent); background: rgba(123,216,143,0.05); color: var(--fg); }
.quiz-option:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.quiz-option.selected { border-color: var(--accent-2); background: rgba(96,165,250,0.1); color: var(--fg); }
.quiz-option.correct { border-color: var(--accent); background: rgba(123,216,143,0.15); color: var(--fg); cursor: default; }
.quiz-option.incorrect { border-color: #ef4444; background: rgba(239,68,68,0.1); color: var(--fg); cursor: default; }
.quiz-option.disabled { pointer-events: none; opacity: 0.6; }
.quiz-option.disabled.correct { opacity: 1; }
.quiz-feedback { margin-top: 12px; padding: 12px 16px; border-radius: 8px; font-size: 14px; display: none; line-height: 1.5; }
.quiz-feedback.show { display: block; }
.quiz-feedback.correct { background: rgba(123,216,143,0.1); color: var(--accent); }
.quiz-feedback.incorrect { background: rgba(239,68,68,0.1); color: #ef4444; }
.quiz-score { background: var(--card); border: 2px solid var(--accent); border-radius: 14px; padding: 32px; text-align: center; margin-top: 32px; display: none; }
.quiz-score.show { display: block; }
.quiz-score h2 { color: var(--fg); margin: 0 0 8px; }
.quiz-score .score-number { font-size: 48px; font-weight: 700; color: var(--accent); }
.quiz-score .score-label { color: var(--muted); font-size: 16px; margin-top: 8px; }
.quiz-score .score-message { color: var(--muted); font-size: 15px; margin-top: 16px; }
.quiz-actions { text-align: center; margin-top: 24px; }
.quiz-submit { display: inline-block; padding: 12px 32px; border-radius: 8px; border: none; background: var(--accent); color: #0d1117; font-weight: 700; font-size: 16px; cursor: pointer; transition: all 0.2s ease; }
.quiz-submit:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(123,216,143,0.3); }
.quiz-submit:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.quiz-submit:disabled { opacity: 0.5; cursor: not-allowed; transform: none; box-shadow: none; }

/* Responsive */
@media (max-width: 768px) {
  .container { padding: 0 16px; }
  .qe-grid { grid-template-columns: 1fr; }
  .lesson-nav { flex-direction: column; }
}
@media (max-width: 600px) {
  .qe-card { padding: 20px; }
  .lesson-link { padding: 16px; gap: 12px; }
  .quiz-question { padding: 16px; }
}