:root{--primary:#17a2b8;--primary-dark:#138496;--secondary:#00394f;--soft:#f8f9fa;--ink:#39454b;--paper:#fff;--line:#dce9ed;--success:#28a745;--warning:#ffc107;--danger:#dc3545}
html{scroll-behavior:smooth}body{overflow-x:hidden;background:#fff;color:#666}.container{max-width:1200px}.navbar{min-height:82px}.navbar-nav .nav-link{margin:0 7px;font-size:16px;font-weight:700}.auth-buttons .btn,.btn-soft{border-radius:25px;font-weight:700}.welcome-text{font-weight:700;white-space:nowrap}
.original-hero{padding:60px 0;background:linear-gradient(rgba(0,58,79,.62),rgba(0,58,79,.62)),url('../../img/header.png') center/cover no-repeat;color:#fff}.original-hero .row{min-height:420px}.original-hero h1{font-size:54px;line-height:1.12;font-weight:800;color:#fff}.original-hero p{font-size:17px;line-height:1.8;max-width:650px}.hero-panel{background:rgba(255,255,255,.95);color:#555;padding:28px;border-radius:18px;box-shadow:0 12px 34px rgba(0,0,0,.18)}.hero-panel h3{color:var(--secondary)}.mini-stat{background:#eef8fa;border-left:4px solid var(--primary);border-radius:10px;padding:12px 14px;margin-bottom:10px}.mini-stat strong{color:var(--secondary);font-size:21px}
.section-block{padding:58px 0}.section-desc{line-height:1.85}.info-box{background:linear-gradient(135deg,#f8fbff,#eef9fb);border-left:5px solid var(--primary);border-radius:16px;padding:22px;box-shadow:0 8px 24px rgba(0,0,0,.06)}.course-card{background:#fff;border-radius:15px;padding:24px;height:100%;box-shadow:0 7px 22px rgba(0,57,79,.08);border:1px solid #edf4f6;transition:.25s}.course-card:hover{transform:translateY(-5px);box-shadow:0 12px 30px rgba(0,57,79,.12)}.course-icon{width:58px;height:58px;border-radius:50%;display:flex;align-items:center;justify-content:center;background:var(--primary);color:#fff;font-size:22px;margin-bottom:18px}.age-pill,.unit-pill{display:inline-block;background:#e9f8fa;color:var(--primary-dark);font-size:12px;font-weight:800;padding:6px 11px;border-radius:18px}.course-card h4{color:var(--secondary);font-weight:800}.course-card p{line-height:1.7}.link-arrow{color:var(--primary);font-weight:800}
.page-header-original{background:linear-gradient(135deg,var(--primary),var(--primary-dark));color:#fff;padding:60px 0}.page-header-original h1{font-size:46px;font-weight:800;color:#fff}.page-header-original p{font-size:17px;line-height:1.8;max-width:850px}.breadcrumbs{font-size:14px;margin-bottom:10px;opacity:.9}.breadcrumbs a{color:#fff;text-decoration:underline}.notice{background:#eef9fb;border-left:4px solid var(--primary);border-radius:9px;padding:15px 18px;margin-bottom:22px}.unit-card{background:#fff;border-radius:16px;box-shadow:0 7px 24px rgba(0,0,0,.06);margin-bottom:25px;overflow:hidden;border:1px solid #eef2f3}.unit-head{padding:20px 24px;background:#f7fbfc;border-bottom:1px solid #e7f0f2;display:flex;justify-content:space-between;align-items:center;gap:15px}.unit-head h3{color:var(--secondary);font-weight:800}.lesson-row{padding:17px 24px;border-bottom:1px solid #eef2f3;display:flex;justify-content:space-between;align-items:center;gap:18px}.lesson-row:last-child{border-bottom:0}.lesson-row strong{color:var(--secondary)}.lesson-meta{font-size:14px;color:#7b878c;line-height:1.55;margin-top:4px}.progressbar{height:10px;background:#e5ecef;border-radius:999px;overflow:hidden}.progressbar span{display:block;height:100%;background:var(--primary);border-radius:999px}
.textbook-layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:28px;align-items:start}.textbook-paper{background:#fff;border-radius:16px;box-shadow:0 8px 26px rgba(0,57,79,.08);overflow:hidden;border:1px solid #eaf0f2}.chapter-ribbon{background:var(--secondary);color:#fff;padding:16px 28px;font-size:14px;font-weight:800;letter-spacing:.6px}.chapter-body{padding:30px}.chapter-body h2,.chapter-body h3,.chapter-body h4{color:var(--secondary);font-weight:800}.chapter-body h2{font-size:28px;margin-top:4px}.chapter-body h3{font-size:21px;margin-top:31px;padding-bottom:8px;border-bottom:2px solid #e7f4f6}.chapter-body p,.chapter-body li{line-height:1.8}.learning-box,.definition-box,.formula-box,.worked-box,.mistake-box,.summary-box,.practice-box{border-radius:12px;padding:19px 21px;margin:18px 0}.learning-box{background:#eef9fb;border-left:5px solid var(--primary)}.definition-box{background:#f8f9fa;border-left:5px solid var(--secondary)}.formula-box{background:#fff9e8;border-left:5px solid var(--warning)}.worked-box{background:#f5fbf6;border-left:5px solid var(--success)}.mistake-box{background:#fff5f5;border-left:5px solid var(--danger)}.summary-box{background:#edf9fb;border:2px solid #c8eaf0}.practice-box{background:#fbfcfd;border:1px solid #dfe8eb}.box-title{font-weight:800;color:var(--secondary);margin-bottom:8px}.math-line{font-family:Georgia,'Times New Roman',serif;font-size:19px;color:#1d333c;background:#fff;padding:10px 13px;border-radius:8px;border:1px solid #e6ecef;margin:9px 0}.worked-step{display:flex;gap:11px;margin:10px 0}.step-no{flex:0 0 28px;width:28px;height:28px;border-radius:50%;background:var(--primary);color:#fff;display:flex;align-items:center;justify-content:center;font-weight:800}.question-list li{margin-bottom:12px}.answer-list{margin-top:10px;padding:14px 18px;background:#f4f8f9;border-radius:9px}.textbook-side{position:sticky;top:20px}.side-card{background:#fff;border-radius:15px;padding:20px;box-shadow:0 8px 24px rgba(0,0,0,.06);margin-bottom:18px;border:1px solid #eaf0f2}.side-card h4{color:var(--secondary);font-weight:800}.keyword-tag{display:inline-block;background:#eef9fb;color:var(--primary-dark);border:1px solid #d6eef2;padding:5px 9px;border-radius:16px;font-size:12px;font-weight:700;margin:3px}.video-wrap{background:#001b24;border-radius:12px;overflow:hidden}.video-wrap video{display:block;width:100%;max-height:540px}.download-lock{font-size:13px;color:#7b878c;margin-top:8px}.btn-round{border-radius:25px;font-weight:700}.searchbox{display:flex;gap:10px;margin-bottom:28px}.searchbox input{flex:1;border:1px solid #ced9dd;border-radius:25px;padding:12px 18px;outline:none}.searchbox input:focus{border-color:var(--primary);box-shadow:0 0 0 3px rgba(23,162,184,.12)}
.auth-shell{padding:65px 15px;background:#f5fafb;min-height:72vh}.auth-card{max-width:900px;margin:auto;background:#fff;border-radius:18px;overflow:hidden;display:grid;grid-template-columns:1fr 1fr;box-shadow:0 12px 35px rgba(0,57,79,.12)}.auth-side{background:linear-gradient(135deg,var(--secondary),#07536f);color:#fff;padding:44px}.auth-side h1{color:#fff;font-weight:800}.auth-form{padding:44px}.auth-form h2{color:var(--secondary);font-weight:800}.field{margin-bottom:17px}.field label{font-weight:700;color:var(--secondary)}.field input,.field select{width:100%;border:1px solid #d4dee2;border-radius:9px;padding:11px 12px}.error{background:#fff1f1;color:#9b2424;border-left:4px solid var(--danger);padding:12px;margin-bottom:15px}.dash-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}.stat{background:#fff;border-radius:14px;padding:22px;box-shadow:0 7px 20px rgba(0,0,0,.06);border-top:4px solid var(--primary)}.stat b{display:block;font-size:30px;color:var(--secondary)}.footer-copy{line-height:1.8;color:#d8e5ea}
@media(max-width:991.98px){.original-hero h1{font-size:42px}.navbar{min-height:auto}.textbook-layout{grid-template-columns:1fr}.textbook-side{position:static}.dash-grid{grid-template-columns:repeat(2,1fr)}.auth-card{grid-template-columns:1fr}.auth-side{padding:30px}.auth-form{padding:30px}}
@media(max-width:576px){.original-hero{padding:40px 0}.original-hero h1{font-size:34px}.page-header-original h1{font-size:34px}.chapter-body{padding:20px}.lesson-row,.unit-head{align-items:flex-start;flex-direction:column}.searchbox{flex-direction:column}.dash-grid{grid-template-columns:1fr}}