/* ===================================================================
   SHARED COURSE MODULE STYLES
   Professional dark-theme course layout with sidebar nav
   =================================================================== */

/* ===== RESET & BASE ===== */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg: #080b12;
  --surface: #0f1320;
  --surface2: #161b2e;
  --surface3: #1c2337;
  --border: #1e2740;
  --border-light: #2a3a5c;
  --text: #e2e8f0;
  --text-secondary: #cbd5e1;
  --dim: #64748b;
  --green: #10b981;
  --red: #ef4444;
  --yellow: #f59e0b;
  --code-bg: #0a0f1a;
  --code-font: 'Cascadia Code', 'Fira Code', 'JetBrains Mono', 'Consolas', monospace;
  --radius: 10px;
  --radius-sm: 6px;
  --radius-lg: 14px;
  --shadow: 0 4px 24px rgba(0,0,0,.4);
  --shadow-sm: 0 2px 8px rgba(0,0,0,.3);
  --nav-width: 270px;
  --transition: .25s cubic-bezier(.4,0,.2,1);
}

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  line-height: 1.75;
  overflow-x: hidden;
  min-height: 100vh;
}

::selection { background: var(--accent, #00d4ff); color: var(--bg); }
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--border-light); }

/* ===== BACKGROUND EFFECTS ===== */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,.015) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.015) 1px, transparent 1px);
  background-size: 60px 60px;
  pointer-events: none;
  z-index: 0;
}

body::after {
  content: '';
  position: fixed;
  top: -30%;
  right: -15%;
  width: 600px;
  height: 600px;
  background: var(--accent, #00d4ff);
  border-radius: 50%;
  filter: blur(200px);
  opacity: .04;
  pointer-events: none;
  z-index: 0;
}

/* ===== SIDEBAR NAVIGATION ===== */
nav {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--nav-width);
  height: 100vh;
  background: var(--surface);
  border-right: 1px solid var(--border);
  padding: 0;
  overflow-y: auto;
  overflow-x: hidden;
  z-index: 100;
  transition: transform var(--transition);
  display: flex;
  flex-direction: column;
}

nav .logo {
  padding: 24px 22px 18px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

nav .logo h2 {
  background: var(--gradient, linear-gradient(135deg, #00d4ff, #7c3aed));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  font-size: 1.2rem;
  font-weight: 800;
  letter-spacing: -.3px;
}

nav .logo span {
  display: block;
  color: var(--dim);
  font-size: .72rem;
  margin-top: 4px;
  letter-spacing: .5px;
  text-transform: uppercase;
}

/* Progress bar in nav */
.progress-wrap {
  padding: 12px 22px 10px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.progress-bar {
  height: 4px;
  background: var(--surface2);
  border-radius: 2px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--gradient, linear-gradient(135deg, #00d4ff, #7c3aed));
  transition: width .5s ease;
  border-radius: 2px;
}

.progress-text {
  font-size: .68rem;
  color: var(--dim);
  margin-top: 5px;
}

/* Home link */
nav .home-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 22px;
  color: var(--dim);
  text-decoration: none;
  font-size: .8rem;
  border-bottom: 1px solid var(--border);
  transition: all var(--transition);
  flex-shrink: 0;
}

nav .home-link:hover {
  color: var(--accent, #00d4ff);
  background: var(--surface2);
}

/* Module links */
nav a.mod-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 11px 22px;
  color: var(--dim);
  text-decoration: none;
  font-size: .82rem;
  transition: all var(--transition);
  border-left: 3px solid transparent;
  white-space: nowrap;
  overflow: hidden;
}

nav a.mod-link span:first-child {
  overflow: hidden;
  text-overflow: ellipsis;
  flex: 1;
}

nav a.mod-link:hover {
  color: var(--text);
  background: var(--surface2);
  border-left-color: var(--accent, #00d4ff);
}

nav a.mod-link.active {
  color: var(--text);
  background: var(--surface2);
  border-left-color: var(--accent, #00d4ff);
  font-weight: 600;
}

/* Difficulty badge in nav */
nav a .diff {
  font-size: .6rem;
  padding: 2px 7px;
  border-radius: 3px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .5px;
  flex-shrink: 0;
}

nav a .d1 { background: rgba(16,185,129,.15); color: var(--green); }
nav a .d2 { background: rgba(245,158,11,.15); color: var(--yellow); }
nav a .d3 { background: rgba(239,68,68,.15); color: var(--red); }

/* Hamburger */
.hamburger {
  display: none;
  position: fixed;
  top: 16px;
  left: 16px;
  z-index: 200;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 1.3rem;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
  line-height: 1;
}

.hamburger:hover {
  border-color: var(--accent, #00d4ff);
  color: var(--accent, #00d4ff);
}

/* ===== MAIN CONTENT ===== */
main {
  position: relative;
  z-index: 1;
  margin-left: var(--nav-width);
  padding: 48px 52px 60px;
  max-width: 920px;
  min-height: 100vh;
}

/* ===== TYPOGRAPHY ===== */
h1 {
  font-size: 2.2rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 8px;
  letter-spacing: -.5px;
  background: var(--gradient, linear-gradient(135deg, #00d4ff, #7c3aed));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

h2 {
  font-size: 1.45rem;
  color: var(--accent, #00d4ff);
  margin: 40px 0 16px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
  font-weight: 700;
  letter-spacing: -.3px;
}

h2:first-of-type {
  margin-top: 30px;
}

h3 {
  font-size: 1.1rem;
  color: var(--text);
  margin: 24px 0 10px;
  font-weight: 600;
}

h4 {
  font-size: 1rem;
  font-weight: 600;
}

p {
  margin-bottom: 16px;
  color: var(--text-secondary);
  font-size: .93rem;
}

strong { color: var(--text); }
em { color: var(--text-secondary); font-style: italic; }

.subtitle {
  color: var(--dim);
  font-size: .95rem;
  margin-bottom: 20px;
  line-height: 1.5;
}

/* ===== BADGES ===== */
.diff-badge {
  display: inline-block;
  padding: 5px 16px;
  border-radius: 20px;
  font-size: .72rem;
  font-weight: 700;
  margin-bottom: 24px;
  text-transform: uppercase;
  letter-spacing: .8px;
}

.diff-badge.easy { background: rgba(16,185,129,.12); color: var(--green); border: 1px solid rgba(16,185,129,.25); }
.diff-badge.medium { background: rgba(245,158,11,.12); color: var(--yellow); border: 1px solid rgba(245,158,11,.25); }
.diff-badge.hard { background: rgba(239,68,68,.12); color: var(--red); border: 1px solid rgba(239,68,68,.25); }

/* ===== CARDS ===== */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px 28px;
  margin: 20px 0;
  box-shadow: var(--shadow-sm);
  transition: border-color var(--transition);
}

.card:hover {
  border-color: var(--border-light);
}

.card.highlight {
  border-left: 4px solid var(--accent, #00d4ff);
  background: linear-gradient(135deg, var(--surface) 0%, rgba(0,212,255,.02) 100%);
}

.card.warn {
  border-left: 4px solid var(--yellow);
  background: linear-gradient(135deg, var(--surface) 0%, rgba(245,158,11,.03) 100%);
}

.card.green {
  border-left: 4px solid var(--green);
  background: linear-gradient(135deg, var(--surface) 0%, rgba(16,185,129,.03) 100%);
}

.card h4 {
  margin-bottom: 12px;
  color: var(--accent, #00d4ff);
  font-size: .95rem;
}

.card.warn h4 { color: var(--yellow); }
.card.green h4 { color: var(--green); }

.card p:last-child { margin-bottom: 0; }

/* ===== CODE BLOCKS ===== */
pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  overflow-x: auto;
  margin: 18px 0;
  font-size: .8rem;
  line-height: 1.7;
  position: relative;
  box-shadow: inset 0 1px 4px rgba(0,0,0,.3);
}

pre .lang-tag {
  position: absolute;
  top: 10px;
  right: 14px;
  color: var(--dim);
  font-size: .65rem;
  text-transform: uppercase;
  letter-spacing: .5px;
  font-family: var(--code-font);
  background: var(--surface2);
  padding: 2px 8px;
  border-radius: 3px;
}

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

p code, .card code, li code, td code, h3 code, h4 code {
  background: var(--code-bg);
  padding: 2px 8px;
  border-radius: 4px;
  font-size: .84em;
  color: var(--accent, #00d4ff);
  border: 1px solid var(--border);
}

/* ===== DIAGRAMS & FLOW ===== */
.diagram {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 30px;
  margin: 22px 0;
  overflow-x: auto;
  box-shadow: var(--shadow-sm);
}

.diagram h4 {
  text-align: center;
  color: var(--accent, #00d4ff);
  margin-bottom: 20px;
  font-size: .95rem;
}

.diagram svg { max-width: 100%; height: auto; }

.flow {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0;
  justify-content: center;
  margin: 10px 0;
}

.flow .box {
  background: var(--surface2);
  border: 1px solid var(--border);
  padding: 12px 18px;
  border-radius: var(--radius);
  font-size: .78rem;
  text-align: center;
  min-width: 100px;
  color: var(--text);
  transition: all var(--transition);
  line-height: 1.4;
}

.flow .box:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

.flow .box small {
  display: block;
  color: var(--dim);
  font-size: .7rem;
  margin-top: 2px;
}

.flow .box.hl  { border-color: var(--accent, #00d4ff); color: var(--accent, #00d4ff); background: rgba(0,212,255,.05); }
.flow .box.g   { border-color: var(--green); color: var(--green); background: rgba(16,185,129,.05); }
.flow .box.r   { border-color: var(--red); color: var(--red); background: rgba(239,68,68,.05); }
.flow .box.y   { border-color: var(--yellow); color: var(--yellow); background: rgba(245,158,11,.05); }
.flow .box.b   { border-color: #38bdf8; color: #38bdf8; background: rgba(56,189,248,.05); }

.flow .arrow {
  color: var(--dim);
  font-size: 1.3rem;
  padding: 0 6px;
  flex-shrink: 0;
  user-select: none;
}

/* ===== TABLES ===== */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0;
  font-size: .84rem;
  background: var(--surface);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border);
}

thead {
  background: var(--surface2);
}

th {
  color: var(--accent, #00d4ff);
  padding: 14px 16px;
  text-align: left;
  font-size: .78rem;
  text-transform: uppercase;
  letter-spacing: .5px;
  font-weight: 700;
  border-bottom: 2px solid var(--border);
}

td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  color: var(--text-secondary);
  vertical-align: top;
}

tr:last-child td { border-bottom: none; }
tr:hover td { background: var(--surface2); }

/* ===== QUIZZES ===== */
.quiz {
  background: var(--surface);
  border: 2px solid var(--accent2, var(--accent, #7c3aed));
  border-radius: var(--radius-lg);
  padding: 28px 30px;
  margin: 32px 0;
  box-shadow: var(--shadow);
}

.quiz h4 {
  color: var(--accent2, var(--accent, #7c3aed));
  margin-bottom: 20px;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  gap: 10px;
}

.quiz h4::before {
  content: '?';
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: var(--accent2, var(--accent, #7c3aed));
  color: var(--bg);
  border-radius: 50%;
  font-size: .8rem;
  font-weight: 800;
  flex-shrink: 0;
}

.quiz-q { margin-bottom: 24px; }

.quiz-q p {
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text);
  font-size: .92rem;
}

.quiz-q label {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  margin: 6px 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--transition);
  font-size: .87rem;
  color: var(--text-secondary);
  background: var(--surface2);
}

.quiz-q label:hover {
  border-color: var(--accent2, var(--accent, #7c3aed));
  background: var(--surface3);
  color: var(--text);
}

.quiz-q label input[type="radio"] {
  accent-color: var(--accent2, var(--accent, #7c3aed));
  flex-shrink: 0;
}

.quiz-q label.correct {
  border-color: var(--green);
  background: rgba(16,185,129,.1);
  color: var(--green);
}

.quiz-q label.wrong {
  border-color: var(--red);
  background: rgba(239,68,68,.1);
  color: var(--red);
}

.quiz-q .explain {
  display: none;
  margin-top: 12px;
  padding: 14px 18px;
  background: var(--surface2);
  border-radius: var(--radius);
  font-size: .84rem;
  border-left: 3px solid var(--accent2, var(--accent, #7c3aed));
  color: var(--text-secondary);
  line-height: 1.6;
}

.quiz-btn {
  background: var(--gradient, linear-gradient(135deg, #00d4ff, #7c3aed));
  color: #fff;
  border: none;
  padding: 12px 36px;
  border-radius: var(--radius);
  cursor: pointer;
  font-weight: 700;
  font-size: .9rem;
  transition: all var(--transition);
  box-shadow: 0 4px 16px rgba(0,0,0,.3);
  letter-spacing: .3px;
}

.quiz-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(0,0,0,.4);
}

.quiz-btn:active { transform: translateY(0); }

.quiz-result {
  margin-top: 16px;
  padding: 16px 20px;
  border-radius: var(--radius);
  font-weight: 700;
  display: none;
  font-size: .95rem;
  text-align: center;
}

/* ===== NAV BUTTONS (Prev/Next) ===== */
.nav-btns {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.nav-btns a,
.nav-btns button {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 12px 28px;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: .88rem;
  transition: all var(--transition);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  box-shadow: var(--shadow-sm);
}

.nav-btns a:hover,
.nav-btns button:hover {
  border-color: var(--accent, #00d4ff);
  color: var(--accent, #00d4ff);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.nav-btns a.primary,
.nav-btns button.primary {
  background: var(--gradient, linear-gradient(135deg, #00d4ff, #7c3aed));
  border: none;
  color: #fff;
  font-weight: 700;
  letter-spacing: .3px;
}

.nav-btns a.primary:hover,
.nav-btns button.primary:hover {
  color: #fff;
  box-shadow: 0 6px 24px rgba(0,0,0,.4);
}

/* ===== LISTS ===== */
ul, ol {
  margin: 12px 0 18px 28px;
}

li {
  margin: 8px 0;
  color: var(--text-secondary);
  font-size: .92rem;
  line-height: 1.7;
}

li strong { color: var(--text); }

li code {
  font-size: .82em;
}

/* ===== VERSUS LAYOUT ===== */
.versus {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 18px 0;
}

.versus > div {
  background: var(--surface2);
  border-radius: var(--radius);
  padding: 20px;
  border: 1px solid var(--border);
  transition: border-color var(--transition);
}

.versus > div:hover {
  border-color: var(--border-light);
}

.versus > div h5 {
  margin-bottom: 10px;
  font-size: .9rem;
  color: var(--accent, #00d4ff);
}

/* ===== TOOLTIP ===== */
.tip {
  position: relative;
  display: inline-block;
  border-bottom: 1px dashed var(--accent, #00d4ff);
  cursor: help;
}

.tip:hover::after {
  content: attr(data-tip);
  position: absolute;
  bottom: 130%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--surface2);
  color: var(--text);
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  font-size: .78rem;
  white-space: nowrap;
  border: 1px solid var(--border);
  z-index: 50;
  box-shadow: var(--shadow);
  max-width: 300px;
}

/* ===== COMPLETE / CELEBRATE CARD ===== */
.complete-card {
  background: linear-gradient(135deg, var(--surface) 0%, rgba(16,185,129,.05) 100%);
  border: 2px solid var(--green);
  border-radius: var(--radius-lg);
  padding: 30px;
  margin: 30px 0;
  text-align: center;
}

.complete-card h3 {
  color: var(--green);
  font-size: 1.3rem;
  margin-bottom: 12px;
}

/* ===== LINKS ===== */
a {
  color: var(--accent, #00d4ff);
  transition: color var(--transition);
}

main a:hover {
  color: var(--accent2, var(--accent, #7c3aed));
}

/* ===== HORIZONTAL RULE ===== */
hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 30px 0;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
  nav {
    transform: translateX(-100%);
  }

  nav.open {
    transform: translateX(0);
    box-shadow: 4px 0 30px rgba(0,0,0,.6);
  }

  .hamburger {
    display: block;
  }

  main {
    margin-left: 0;
    padding: 24px 20px 40px;
    padding-top: 68px;
  }

  h1 { font-size: 1.7rem; }
  h2 { font-size: 1.25rem; }

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

  pre { padding: 16px; font-size: .75rem; }

  .nav-btns { flex-direction: column; }
  .nav-btns a, .nav-btns button { text-align: center; justify-content: center; }

  .flow .box { min-width: 80px; padding: 10px 12px; font-size: .72rem; }
}

@media (max-width: 500px) {
  main { padding: 16px 14px 30px; padding-top: 60px; }
  h1 { font-size: 1.4rem; }
  .card { padding: 18px 16px; }
  pre { padding: 12px; font-size: .72rem; }
  table { font-size: .76rem; }
  th, td { padding: 8px 10px; }
}

/* ===== ANIMATIONS ===== */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

main > h1,
main > .subtitle,
main > .diff-badge {
  animation: fadeIn .5s ease both;
}

main > h2 {
  animation: fadeIn .4s ease both;
}

main > .card,
main > .diagram,
main > pre,
main > .quiz,
main > table {
  animation: fadeIn .5s ease both;
}

/* ===== PRINT ===== */
@media print {
  nav, .hamburger, .quiz-btn, .nav-btns { display: none !important; }
  main { margin-left: 0; padding: 20px; max-width: 100%; }
  body { background: #fff; color: #000; }
  .card, .diagram, pre { border: 1px solid #ccc; box-shadow: none; }
  h1, h2 { -webkit-text-fill-color: initial; background: none; color: #000; }
}