/* =============================================
   Year 10 Mathematics - Unit 4 Theme
   Statistics and Probability
   NESA Stage 5 Core + Paths | 2022 Syllabus
   ============================================= */

:root {
  --bg: #f5f7fb;
  --surface: #ffffff;
  --text: #0f172a;
  --text-muted: #475569;
  --text-light: #64748b;
  --border: #dde3ee;
  --primary: #059669;
  --primary-mid: #047857;
  --primary-light: #d1fae5;
  --accent: #0d9488;
  --accent-dark: #0f766e;
  --accent-light: #ccfbf1;
  --amber: #d97706;
  --amber-light: #fffbeb;
  --green: #16a34a;
  --green-light: #dcfce7;
  --coral: #e11d48;
  --coral-light: #ffe4e6;
  --radius: 16px;
  --radius-sm: 12px;
  --radius-xs: 10px;
  --shadow: 0 4px 16px rgba(15,23,42,0.04);
}

body { font-family: 'DM Sans',sans-serif; background: var(--bg); color: var(--text); line-height: 1.65; }
h1,h2,h3,h4,h5,h6 { font-family: 'Nunito',sans-serif; font-weight: 700; }
code,.mono,.katex { font-family: 'DM Mono',monospace; }

.skip-link { position: absolute; top: -40px; left: 0; background: var(--primary); color: #fff; padding: 8px 16px; z-index: 100; transition: top 0.3s; }
.skip-link:focus { top: 0; }

.progress-bar-wrap { position: fixed; top: 0; left: 0; right: 0; height: 4px; background: rgba(0,0,0,0.06); z-index: 50; }
.progress-bar-fill { height: 100%; background: linear-gradient(90deg,var(--primary),var(--accent)); width: 0%; transition: width 0.2s ease; }

.section-nav { position: fixed; right: 18px; top: 50%; transform: translateY(-50%); display: flex; flex-direction: column; gap: 8px; z-index: 40; }
.section-nav a { width: 10px; height: 10px; border-radius: 50%; background: var(--border); transition: all 0.2s; }
.section-nav a.active { background: var(--primary); transform: scale(1.3); }
@media (max-width:900px) { .section-nav { display: none; } }

.hero { background: linear-gradient(135deg,#064e3b 0%,#0f766e 50%,var(--primary) 100%); color: #fff; padding: 48px 42px 42px; border-radius: 0 0 var(--radius) var(--radius); margin-bottom: 8px; }
.hero-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 20px; max-width: 1100px; margin: 0 auto; }
.hero h1 { color: #fff; font-size: 40px; line-height: 1.08; margin: 0 0 12px; letter-spacing: -0.5px; }
.hero-desc { color: rgba(255,255,255,0.92); font-size: 17px; max-width: 720px; line-height: 1.6; margin: 0; }
.hero-badge-row { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 14px; }
.badge { display: inline-flex; padding: 5px 14px; border-radius: 999px; background: rgba(255,255,255,0.14); color: #fff; font-size: 12px; font-weight: 600; border: 1px solid rgba(255,255,255,0.22); backdrop-filter: blur(4px); }
.badge-maths { background: rgba(45,212,191,0.25); border-color: rgba(45,212,191,0.4); }
.hero-emoji { font-size: 56px; line-height: 1; flex-shrink: 0; opacity: 0.9; }

.mode-banner { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 18px 24px; margin: 20px auto; max-width: 1100px; display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.mode-toggle { display: flex; gap: 6px; }
.mode-btn { padding: 8px 18px; border-radius: 999px; border: 1px solid var(--border); background: transparent; cursor: pointer; font-size: 14px; font-weight: 500; color: var(--text-muted); transition: all 0.2s; }
.mode-btn.active { background: var(--primary); color: #fff; border-color: var(--primary); }

.timer-bar { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 14px 24px; margin: 20px auto; max-width: 1100px; display: flex; align-items: center; gap: 16px; }
#timerDisplay { font-family: 'DM Mono',monospace; font-size: 22px; font-weight: 600; color: var(--text); letter-spacing: 1px; }

.phase-strip { display: flex; align-items: center; gap: 8px; padding: 18px 24px; margin: 0 auto; max-width: 1100px; }
.phase-btn { padding: 10px 22px; border-radius: 999px; border: 1px solid var(--border); background: var(--surface); cursor: pointer; font-size: 14px; font-weight: 600; color: var(--text-muted); transition: all 0.2s; }
.phase-btn.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.phase-arrow { color: var(--text-light); font-size: 18px; }

.phase { display: none; }
.phase.active { display: block; }

.content-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px 32px; margin: 20px auto; max-width: 1100px; box-shadow: var(--shadow); }
.content-card h2 { font-size: 22px; margin: 0 0 14px; color: var(--text); }
.content-card h3 { font-size: 17px; margin: 20px 0 10px; color: var(--text); }
.content-card p, .content-card li { font-size: 15px; line-height: 1.7; color: var(--text-muted); }
.content-card ul, .content-card ol { margin: 10px 0; padding-left: 22px; }
.content-card li { margin-bottom: 6px; }

.worksheet-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 28px; margin: 20px auto; max-width: 1100px; display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 14px; }
.worksheet-actions { display: flex; gap: 10px; flex-wrap: wrap; }

.interactive-wrap { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; margin: 20px auto; max-width: 1100px; }
.interactive-wrap iframe { width: 100%; height: 420px; border: none; border-radius: var(--radius-sm); }

.mcq { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 28px; margin: 16px auto; max-width: 1100px; }
.mcq-header { display: flex; gap: 8px; margin-bottom: 10px; }
.mcq-q { font-size: 16px; font-weight: 600; color: var(--text); margin: 0 0 14px; }
.mcq-options { display: flex; flex-direction: column; gap: 8px; margin-bottom: 14px; }
.mcq-opt { display: flex; align-items: center; gap: 10px; padding: 12px 16px; border: 1px solid var(--border); border-radius: var(--radius-xs); cursor: pointer; transition: all 0.15s; font-size: 15px; color: var(--text-muted); background: var(--surface); }
.mcq-opt:hover { border-color: var(--primary); background: var(--primary-light); }
.mcq-opt input { accent-color: var(--primary); width: 18px; height: 18px; cursor: pointer; }
.mcq-explanation { display: none; margin-top: 14px; padding: 16px 18px; background: #f8fafc; border-radius: var(--radius-sm); border-left: 4px solid var(--primary); font-size: 14px; color: var(--text-muted); line-height: 1.6; }

.saq { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 28px; margin: 16px auto; max-width: 1100px; }
.saq-header { display: flex; gap: 8px; margin-bottom: 10px; }
.saq-q { font-size: 16px; font-weight: 600; color: var(--text); margin: 0 0 14px; }
.answer-wrap { position: relative; }
.answer-textarea { width: 100%; min-height: 160px; padding: 16px; border: 1px solid var(--border); border-radius: var(--radius-sm); font-family: 'DM Sans',sans-serif; font-size: 15px; line-height: 1.6; resize: vertical; background: var(--surface); color: var(--text); }
.answer-textarea:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-light); }
.autosave-indicator { position: absolute; top: 10px; right: 14px; font-size: 11px; color: var(--text-light); background: rgba(255,255,255,0.9); padding: 2px 8px; border-radius: 4px; }

.review-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px 32px; margin: 20px auto; max-width: 1100px; }
.review-items { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; margin-top: 16px; }
.review-item { background: #f8fafc; border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 14px 16px; }
.review-item h4 { margin: 0 0 6px; font-size: 14px; color: var(--text); }
.review-item p { margin: 0; font-size: 13px; color: var(--text-muted); }

.continue-next { text-align: center; margin: 28px auto; max-width: 1100px; }
.lesson-footer { text-align: center; padding: 28px 24px; color: var(--text-light); font-size: 13px; border-top: 1px solid var(--border); margin-top: 20px; }
.lesson-footer a { color: var(--primary); text-decoration: none; }
.lesson-footer a:hover { text-decoration: underline; }

.btn { display: inline-flex; align-items: center; gap: 6px; padding: 10px 20px; border-radius: 999px; border: none; background: var(--primary); color: #fff; font-size: 14px; font-weight: 600; cursor: pointer; text-decoration: none; transition: all 0.2s; }
.btn:hover { background: var(--primary-mid); transform: translateY(-1px); }
.btn-outline { background: transparent; color: var(--primary); border: 1px solid var(--primary); }
.btn-outline:hover { background: var(--primary-light); }

.think-first { background: var(--primary-light); border-left: 4px solid var(--primary); padding: 16px 20px; border-radius: 0 var(--radius-sm) var(--radius-sm) 0; margin: 16px 0; }
.think-first p { margin: 0; font-size: 15px; color: var(--text); }
.think-first strong { color: var(--primary); }

.fade-up { opacity: 0; transform: translateY(12px); transition: opacity 0.4s ease, transform 0.4s ease; }
.fade-up.visible { opacity: 1; transform: translateY(0); }

@media (max-width: 900px) {
  .hero { padding: 36px 24px; }
  .hero h1 { font-size: 30px; }
  .hero-top { flex-direction: column; }
  .content-card, .mcq, .saq, .interactive-wrap, .worksheet-card, .review-card { margin: 14px 16px; padding: 20px; }
}