* { margin: 0; padding: 0; box-sizing: border-box; }
:root { --primary: #7c3aed; --secondary: #06b6d4; --dark: #0f172a; --card: #1e293b; --correct: #10b981; --wrong: #ef4444; }
body { font-family: 'Inter', 'Segoe UI', sans-serif; background: linear-gradient(135deg, #0f172a, #1e293b); min-height: 100vh; color: #e2e8f0; }
.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
header { background: rgba(15,23,42,0.95); backdrop-filter: blur(15px); padding: 20px 0; position: sticky; top: 0; z-index: 100; border-bottom: 2px solid var(--primary); }
.logo { font-size: 28px; font-weight: 800; background: linear-gradient(90deg, var(--primary), var(--secondary)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
nav a { color: #94a3b8; text-decoration: none; margin-left: 25px; font-weight: 600; }
nav a:hover { color: #fff; }
.hero { background: linear-gradient(135deg, var(--primary), #4c1d95); padding: 80px 0; text-align: center; }
.hero h1 { font-size: 48px; color: #fff; margin-bottom: 10px; }
.hero p { font-size: 18px; color: #c4b5fd; }
main { padding: 50px 0; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 20px; }
.card { background: var(--card); border-radius: 16px; padding: 24px; text-align: center; transition: all 0.3s; border: 1px solid #334155; }
.card:hover { transform: translateY(-5px); border-color: var(--secondary); box-shadow: 0 10px 30px rgba(124,58,237,0.2); }
.card .num { background: var(--primary); color: #fff; width: 36px; height: 36px; border-radius: 50%; display: inline-flex; align-items: center; justify-content: center; font-weight: 700; margin-bottom: 12px; }
.card h3 { color: #f1f5f9; font-size: 15px; margin-bottom: 8px; }
.card a { display: inline-block; padding: 10px 22px; background: linear-gradient(135deg, var(--primary), var(--secondary)); color: #fff; text-decoration: none; border-radius: 20px; font-weight: 600; font-size: 13px; }
footer { background: #0f172a; padding: 30px 0; text-align: center; border-top: 1px solid #334155; }
.q-page { background: var(--card); border-radius: 20px; padding: 40px; margin: 30px auto; max-width: 900px; }
.q-page h1 { color: #f1f5f9; font-size: 26px; margin-bottom: 25px; text-align: center; }
.q-box { background: #0f172a; padding: 25px; border-radius: 12px; margin-bottom: 20px; }
.q-box p { font-size: 18px; line-height: 1.8; color: #e2e8f0; }
.q-box .math { font-family: 'Times New Roman', serif; font-size: 22px; color: #c4b5fd; display: block; margin: 15px 0; text-align: center; }
.options { display: grid; gap: 12px; }
.opt { background: #334155; padding: 15px 20px; border-radius: 10px; cursor: pointer; transition: all 0.2s; border: 2px solid transparent; }
.opt:hover { background: #475569; }
.opt.correct { background: rgba(16,185,129,0.2); border-color: var(--correct); }
.opt.wrong { background: rgba(239,68,68,0.2); border-color: var(--wrong); }
.opt.selected { border-color: var(--primary); }
.btn { padding: 14px 28px; background: linear-gradient(135deg, var(--primary), var(--secondary)); color: #fff; border: none; border-radius: 25px; font-weight: 700; cursor: pointer; margin: 10px 5px; }
.btn:hover { box-shadow: 0 8px 20px rgba(124,58,237,0.4); }
.result { padding: 20px; border-radius: 12px; margin-top: 20px; text-align: center; font-size: 18px; }
.result.correct { background: rgba(16,185,129,0.2); border: 1px solid var(--correct); }
.result.wrong { background: rgba(239,68,68,0.2); border: 1px solid var(--wrong); }
.explanation { background: rgba(6,182,212,0.1); padding: 20px; border-radius: 12px; margin-top: 20px; border-left: 4px solid var(--secondary); }
.explanation h3 { color: var(--secondary); margin-bottom: 10px; }
.explanation p { color: #94a3b8; line-height: 1.7; }
.back-link { color: var(--secondary); text-decoration: none; font-weight: 600; }
a[href^="privacy"], a[href^="terms"] { color: #64748b; margin: 0 12px; }