:root{--primary:#2563eb;--primary-light:#eff6ff;--accent:#f59e0b;--dark:#0f172a;--muted:#64748b;--radius:14px}*{font-family:'Nunito',sans-serif}body{background:#f8fafc;color:var(--dark)}.navbar{background:#fff;border-bottom:1px solid #e2e8f0}.navbar-brand{font-weight:800;font-size:1.3rem;color:var(--primary)!important}.nav-link{font-weight:600;color:#334155!important}.nav-link:hover{color:var(--primary)!important}.hero{background:linear-gradient(135deg,#1e3a8a 0%,#2563eb 60%,#3b82f6 100%);padding:72px 0 56px;color:#fff;position:relative;overflow:hidden}.hero:before{content:'';position:absolute;top:0;right:0;width:33.333%;height:100%;pointer-events:none;opacity:.28;background-image:linear-gradient(rgba(255,255,255,.35) 1px,transparent 1px),linear-gradient(90deg,rgba(255,255,255,.35) 1px,transparent 1px);background-size:42px 42px;-webkit-mask-image:linear-gradient(to right,transparent 0%,#000 35%,#000 100%);mask-image:linear-gradient(to right,transparent 0%,#000 35%,#000 100%)}.hero .container{position:relative;z-index:1}.free-badge{display:inline-flex;align-items:center;gap:6px;background:rgba(34,197,94,.2);color:#86efac;border:1px solid rgba(34,197,94,.4);border-radius:50px;padding:5px 16px;font-size:.82rem;font-weight:800;margin-bottom:20px}.hero h1{font-size:clamp(2rem,5vw,2.2rem);font-weight:800;line-height:1.15}.hero p{font-size:1.1rem;opacity:.88}.section-title{font-size:1.9rem;font-weight:800}.section-sub{color:var(--muted);max-width:680px;margin:0 auto}.subject-card,.feature-card,.content-area,.test-card{background:#fff;border:1px solid #e2e8f0;border-radius:var(--radius);box-shadow:0 8px 28px rgba(15,23,42,.05)}.subject-card{padding:24px 20px;transition:all .2s;height:100%;text-decoration:none;color:var(--dark);display:block}.subject-card:hover{border-color:var(--primary);box-shadow:0 8px 32px rgba(37,99,235,.1);transform:translateY(-4px);color:var(--dark)}.subject-icon{width:48px;height:48px;border-radius:12px;display:flex;align-items:center;justify-content:center;font-size:1.3rem;margin-bottom:14px}.subject-card h5{font-weight:800;font-size:1rem}.subject-card p{font-size:.86rem;color:var(--muted);margin:0}.badge-required,.badge-profile{font-size:.72rem;font-weight:800;border-radius:50px;padding:2px 10px}.badge-required{background:#fef3c7;color:#92400e}.badge-profile{background:#eff6ff;color:#1d4ed8}.feature-card{padding:26px;height:100%}.step-number{width:48px;height:48px;border-radius:50%;background:var(--primary-light);color:var(--primary);font-weight:800;display:flex;align-items:center;justify-content:center}.test-section{background:var(--primary-light)}.content-area{padding:18px}.explain-area{background:#fff;border:1px solid #e2e8f0;border-radius:var(--radius);padding:18px;box-shadow:0 8px 28px rgba(15,23,42,.06);top:90px;max-height:calc(100vh - 120px);overflow:auto}.option-item{border:1px solid #e2e8f0;border-radius:10px;padding:12px;margin-bottom:10px;cursor:pointer;transition:.15s}.option-item:hover{background:#f8fbff;border-color:#bfdbfe}.option-item.correct{border-color:#16a34a;background:#f0fdf4}.option-item.wrong{border-color:#dc2626;background:#fef2f2}.option-item.selected{border-color:#2563eb;background:#eff6ff}.question-card.locked .option-item{pointer-events:none}.step{background:#f8fafc;border:1px solid #e2e8f0;border-radius:10px;padding:10px 12px;margin:10px 0}.step-title{font-weight:800;margin-bottom:6px}.math-chip{display:inline-block;background:#eef4ff;border-radius:10px;padding:6px 10px;margin:6px 0}.seg-progress{height:10px;display:flex;gap:4px;border-radius:999px;overflow:hidden}.seg{height:100%;border-radius:999px}.bg-success{background:#22c55e!important}.bg-danger{background:#ef4444!important}.bg-info{background:#38bdf8!important}.badge-dot{width:10px;height:10px;border-radius:50%;display:inline-block}.badge-dot.ok{background:#16a34a}.badge-dot.bad{background:#dc2626}#explainFab{position:fixed;left:50%;bottom:16px;transform:translateX(-50%);z-index:1080;border-radius:999px;padding:10px 14px;box-shadow:0 10px 25px rgba(0,0,0,.18);display:none}@media(max-width:991.98px){#right-col{display:none!important}}@media(min-width:992px){#explainFab{display:none!important}}footer{background:var(--dark);color:#94a3b8}footer a{color:#94a3b8;text-decoration:none}footer a:hover{color:#fff}.footer-brand{font-size:1.2rem;font-weight:800;color:#fff}