:root{--brand:#0c82eb;--brand2:#075bb5;--nav:#071f43;--ink:#0f172a;--muted:#64748b;--bg:#f8fafc;--line:#e2e8f0;--green:#16a34a}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;font-family:'Plus Jakarta Sans',Arial,sans-serif;background:var(--bg);color:var(--ink)}a{text-decoration:none;color:inherit}.site-header{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.96);backdrop-filter:blur(12px);border-bottom:1px solid #edf2f7;box-shadow:0 4px 18px rgba(15,23,42,.05)}.nav-shell{max-width:1280px;margin:auto;padding:12px 24px;display:flex;align-items:center;gap:30px}.logo-lockup{display:flex;align-items:center;gap:10px;min-width:190px}.logo-mark,.login-badge{display:grid;place-items:center;background:linear-gradient(135deg,var(--nav),var(--brand));color:#fff;font-weight:800;border-radius:13px}.logo-mark{width:44px;height:44px}.logo-lockup b{display:block;font-size:17px;color:#082654;letter-spacing:.02em}.logo-lockup small{display:block;font-size:9px;letter-spacing:.18em;text-transform:uppercase;color:#94a3b8;font-weight:800}.main-nav{display:flex;align-items:center;gap:23px;flex:1;justify-content:center}.main-nav a{font-size:13px;font-weight:700;color:#526177;white-space:nowrap;transition:.2s}.main-nav a:hover,.main-nav a.active{color:var(--brand)}.main-nav a.active{position:relative}.main-nav a.active:after{content:"";position:absolute;left:0;right:0;bottom:-18px;height:3px;border-radius:4px;background:var(--brand)}.account-nav{display:flex;align-items:center;gap:12px;font-size:12px;font-weight:700;white-space:nowrap}.account-nav a{color:#475569}.account-nav a:hover{color:var(--brand)}.user-name{max-width:100px;overflow:hidden;text-overflow:ellipsis}.nav-login,.soft-btn{background:#eff6ff!important;color:#075bb5!important;padding:9px 13px;border-radius:10px}.wrap{max-width:1280px;margin:auto;padding:30px 24px 50px}.hero{background:radial-gradient(circle at 90% 0,rgba(56,189,248,.25),transparent 35%),linear-gradient(135deg,#061d3d,#075bb5 70%,#0c82eb);color:#fff;border-radius:28px;padding:38px 42px;margin-bottom:34px;display:flex;justify-content:space-between;align-items:center;box-shadow:0 18px 45px rgba(7,47,100,.16)}.hero h1{font-size:34px;margin:12px 0 8px;letter-spacing:-.03em}.hero p{color:#cbd5e1;margin:0}.pill,.eyebrow{font-size:11px;font-weight:800;letter-spacing:.12em;text-transform:uppercase}.pill{display:inline-flex;padding:7px 11px;border:1px solid rgba(255,255,255,.25);border-radius:999px;background:rgba(255,255,255,.08)}.hero-stat{display:flex;align-items:baseline;gap:7px;background:rgba(255,255,255,.1);border:1px solid rgba(255,255,255,.16);padding:18px 22px;border-radius:18px}.hero-stat b{font-size:36px}.hero-stat span{font-size:12px;color:#dbeafe}.section-title{display:flex;justify-content:space-between;align-items:end;margin:30px 0 16px}.section-title h2{font-size:25px;margin:5px 0}.section-title p{margin:5px 0}.eyebrow{color:var(--brand)}.path-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:13px}.path-card,.chapter-card,.problem-row,.panel{background:#fff;border:1px solid var(--line);box-shadow:0 7px 25px rgba(15,23,42,.035)}.path-card{min-height:150px;border-radius:18px;padding:20px;display:flex;gap:14px;transition:.2s}.path-card>span,.chapter-icon{flex:0 0 38px;height:38px;border-radius:12px;display:grid;place-items:center;background:#eff6ff;color:var(--brand2);font-weight:800}.path-card b{font-size:15px}.path-card p,.chapter-card p,.problem-row p{font-size:12px;color:var(--muted);line-height:1.55}.path-card.primary:hover,.chapter-card:hover,.problem-row:hover{transform:translateY(-2px);border-color:#bfdbfe;box-shadow:0 12px 30px rgba(12,130,235,.09)}.path-card.locked{opacity:.78}.chapter-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:14px}.chapter-card{border-radius:18px;padding:18px;display:flex;gap:14px;align-items:center;transition:.2s}.chapter-card>div:last-child{flex:1}.chapter-card p{margin:6px 0}.progress{height:5px;background:#eaf0f6;border-radius:999px;overflow:hidden}.progress i{display:block;height:100%;background:linear-gradient(90deg,#0c82eb,#22c55e)}.problem-list{display:grid;gap:9px}.problem-row{display:grid;grid-template-columns:46px 1fr 30px;align-items:center;gap:14px;border-radius:15px;padding:14px 18px;transition:.2s}.problem-row b{font-size:14px}.problem-row p{margin:4px 0 0}.status-dot{width:38px;height:38px;display:grid;place-items:center;border-radius:50%;background:#eff6ff;color:var(--brand);font-size:12px;font-weight:800}.completed .status-dot{background:#dcfce7;color:#15803d}.go{color:#94a3b8;font-size:20px}.back{font-size:12px;font-weight:700;color:var(--brand)}.footer{text-align:center;color:#94a3b8;font-size:11px;padding:28px}.login-shell{max-width:1120px;margin:55px auto;padding:20px;display:grid;grid-template-columns:1.05fr .75fr;gap:55px;align-items:center}.login-intro{padding:35px}.login-intro .pill{color:#075bb5;background:#eff6ff;border-color:#dbeafe}.login-intro h1{font-size:48px;line-height:1.08;letter-spacing:-.045em;margin:20px 0}.login-intro h1 em{font-style:normal;color:var(--brand)}.login-intro>p{color:var(--muted);line-height:1.8;max-width:600px}.feature-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:25px}.feature-row span{background:#fff;border:1px solid var(--line);padding:10px 12px;border-radius:12px;font-size:11px;font-weight:700;color:#475569}.login-card{background:#fff;border:1px solid var(--line);border-radius:24px;padding:32px;box-shadow:0 24px 60px rgba(15,23,42,.1)}.login-badge{width:54px;height:54px;margin-bottom:18px}.login-card h2{font-size:23px;margin:0 0 8px}.login-card label{display:block;font-size:12px;font-weight:800;margin:18px 0 7px}.field,.select{width:100%;border:1px solid #cbd5e1;background:#fff;padding:12px 13px;border-radius:11px;font:inherit;font-size:13px;outline:none}.field:focus,.select:focus{border-color:#60a5fa;box-shadow:0 0 0 3px #dbeafe}.btn{border:0;border-radius:11px;padding:11px 15px;background:var(--brand);color:#fff;font-weight:800;cursor:pointer;font-family:inherit}.btn:hover{filter:brightness(.95)}.btn.full{width:100%;margin-top:22px;padding:13px}.btn.success{background:#16a34a}.btn.secondary{background:#fff;color:#334155;border:1px solid var(--line)}.help{text-align:center;font-size:11px;color:#94a3b8;margin:20px 0 0}.alert{padding:11px;border-radius:10px;font-size:12px;margin:15px 0}.bad{color:#b91c1c;background:#fef2f2}.ok{color:#15803d}.muted{color:var(--muted);font-size:12px}.problem-toolbar{display:flex;justify-content:space-between;font-size:12px;font-weight:700;color:#64748b;margin-bottom:14px}.judge{display:grid;grid-template-columns:.9fr 1.1fr;gap:18px}.panel{border-radius:18px;padding:22px}.statement h1{font-size:30px;margin:10px 0}.statement-text{line-height:1.75}.panel h3{font-size:13px;margin:20px 0 8px}.io{background:#f8fafc;border:1px solid var(--line);padding:12px;border-radius:10px;white-space:pre-wrap;font:12px/1.55 Consolas,monospace}.editor{width:100%;min-height:450px;background:#0b1220;color:#e2e8f0;border:0;border-radius:13px;padding:16px;font:13px/1.55 Consolas,monospace;tab-size:4;margin-top:13px}.row{display:flex;gap:9px;align-items:center;flex-wrap:wrap}.row .select{width:auto;min-width:130px}.result-title{display:flex;justify-content:space-between;align-items:center}.result-title h3{margin-bottom:8px}.card{background:#fff;border:1px solid var(--line);border-radius:16px;padding:18px}.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px}@media(max-width:1050px){.main-nav{display:none}.path-grid{grid-template-columns:repeat(2,1fr)}.chapter-grid{grid-template-columns:repeat(2,1fr)}}@media(max-width:800px){.judge,.login-shell{grid-template-columns:1fr}.login-intro{padding:10px}.login-intro h1{font-size:35px}.hero{padding:28px;align-items:flex-start;gap:20px}.hero-stat{display:none}.editor{min-height:340px}.user-name{display:none}}@media(max-width:560px){.nav-shell{padding:10px 14px}.logo-lockup{min-width:auto}.logo-lockup span:last-child{display:none}.account-nav{margin-left:auto}.path-grid,.chapter-grid{grid-template-columns:1fr}.wrap{padding:20px 14px}.hero h1{font-size:26px}.problem-row{grid-template-columns:42px 1fr 20px}.problem-row p{display:none}}

/* 2026-09-29 dashboard/admin refresh */
.compact{min-height:170px}.stat-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:16px;margin:22px 0}.stat-card,.action-card{background:#fff;border:1px solid #e7eaf0;border-radius:18px;padding:22px;box-shadow:0 8px 24px rgba(20,30,60,.05)}.stat-card b{display:block;font-size:32px}.stat-card span,.action-card p{color:#667085}.admin-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:16px;margin:22px 0}.action-card{display:block;text-decoration:none;color:#172033}.action-card b{font-size:18px}.two-col{display:grid;grid-template-columns:minmax(300px,420px) 1fr;gap:20px}.narrow{max-width:820px;margin:24px auto}.panel label{display:block;font-weight:600;margin:12px 0}.panel label .select{display:block;width:100%;margin-top:6px}.table-wrap{overflow:auto}table{width:100%;border-collapse:collapse}th,td{text-align:left;padding:12px;border-bottom:1px solid #edf0f5}td small{display:block;color:#98a2b3}.stars{color:#f59e0b;letter-spacing:1px}.form-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px 16px}.form-grid label{margin:0}.span2{grid-column:1/-1}.textarea{min-height:95px;resize:vertical}.history{border-top:1px solid #edf0f5}.history>div{display:flex;justify-content:space-between;gap:12px;padding:10px 0;border-bottom:1px solid #edf0f5}.history span{color:#667085;font-size:13px}@media(max-width:850px){.stat-grid{grid-template-columns:1fr 1fr}.admin-grid,.two-col,.form-grid{grid-template-columns:1fr}.span2{grid-column:auto}.history>div{display:block}}

/* BITMASTER official logo */
.brand-logo{width:72px;height:58px;object-fit:contain;display:block;border-radius:10px}.logo-lockup{min-width:96px}.login-brand{margin-bottom:18px}.login-brand-logo{width:110px;height:110px;object-fit:contain;display:block;border-radius:16px}@media(max-width:560px){.brand-logo{width:58px;height:48px}.logo-lockup{min-width:auto}.login-brand-logo{width:92px;height:92px}}
fieldset{border:1px solid #dfe6ee;border-radius:12px;padding:12px 14px;margin:12px 0}legend{font-weight:700;padding:0 6px}.check-inline{display:inline-flex!important;align-items:center;gap:5px;margin:5px 10px 5px 0!important}.student-manage{padding:14px 0;border-bottom:1px solid #edf1f5}.student-manage form{margin-top:8px}.level-form{white-space:nowrap}.level-form .soft-btn{padding:6px 10px}

/* 2026-09-29 · standardized LMS management UI */
.module-nav{display:flex;gap:8px;flex-wrap:wrap;margin:18px 0 24px}.module-nav a{padding:10px 15px;border-radius:12px;background:#eef6ff;color:#075dbd;text-decoration:none;font-weight:700}.module-nav a.active{background:#087cf0;color:#fff;box-shadow:0 8px 22px rgba(8,124,240,.18)}
.filter-bar{display:flex;gap:14px;align-items:end;flex-wrap:wrap}.filter-bar label{min-width:190px;margin:0}.filter-bar .grow{flex:1;min-width:240px}.filter-bar .btn{height:48px}
.progress-table{display:grid;gap:10px}.progress-row{display:flex;gap:16px;align-items:center;padding:17px 18px;border:1px solid #dfe8f3;border-radius:16px;text-decoration:none;color:inherit;background:#fff;transition:.18s}.progress-row:hover{transform:translateY(-1px);box-shadow:0 10px 28px rgba(15,54,92,.08);border-color:#bddcff}.avatar{width:44px;height:44px;display:grid;place-items:center;border-radius:50%;background:#edf6ff;color:#087cf0;font-weight:800}.progress-main{flex:1;min-width:0}.progress-head{display:flex;justify-content:space-between;gap:12px}.progress-track{height:7px;background:#eaf0f6;border-radius:99px;overflow:hidden;margin-top:9px}.progress-track i{display:block;height:100%;background:linear-gradient(90deg,#0b65c8,#1598ff);border-radius:99px}.small{font-size:13px}.empty-state{padding:32px;text-align:center;color:#73859a;background:#f8fbff;border-radius:14px}
.class-card{border:1px solid #dfe8f3;border-radius:18px;padding:18px;margin:14px 0;background:#fff}.class-card-head{display:flex;justify-content:space-between;gap:12px;align-items:start}.class-card h3{margin:0 0 4px}.inline-form,.inline-edit,.add-member{display:flex;gap:8px;align-items:center}.inline-edit{margin:12px 0}.inline-edit .select,.add-member .select{flex:1}.member-list{border-top:1px solid #edf1f5;margin-top:10px}.member-row{display:flex;justify-content:space-between;gap:12px;align-items:center;padding:11px 2px;border-bottom:1px solid #edf1f5}.danger-link{border:0;background:transparent;color:#c33434;font-weight:700;cursor:pointer;padding:7px 8px;border-radius:8px}.danger-link:hover{background:#fff0f0}.add-member{margin-top:14px}
@media(max-width:760px){.filter-bar label,.filter-bar .grow{width:100%;min-width:0}.filter-bar .btn{width:100%}.progress-row{align-items:flex-start}.progress-head{display:block}.class-card-head,.member-row,.inline-edit,.add-member{align-items:stretch;flex-direction:column}.module-nav{overflow-x:auto;flex-wrap:nowrap}.module-nav a{white-space:nowrap}}
/* CRUD usability */
details > summary.soft-btn{display:inline-block;cursor:pointer;list-style:none;margin:4px 0}details > summary::-webkit-details-marker{display:none}.mini-edit{display:grid;gap:8px;min-width:260px;padding:10px 0}.inline-form{display:inline-flex;gap:6px;align-items:center}.student-manage{gap:10px;flex-wrap:wrap}.student-manage details{margin-left:auto}
/* =====================================
   KẾT QUẢ CHẠY TEST
   ===================================== */

/* Chạy test thành công - xanh BITMASTER */
.io.ok {
    color: #0c82eb !important;
    background: #eff6ff !important;
    border-color: #bfdbfe !important;
}

/* Chạy test có lỗi - đỏ */
.io.bad {
    color: #b91c1c !important;
    background: #fef2f2 !important;
    border-color: #fecaca !important;
}
.login-heading {
    width: 100%;
    text-align: center;
}

.login-heading img {
    display: block;
    margin: 0 auto 24px;
}

.login-heading h1 {
    margin: 0 0 8px;
    text-align: center;
}

.login-heading .muted {
    margin: 0 auto 24px;
    text-align: center;
}/* Production learning browser: horizontal folders -> topics -> problems */
.course-tabs{display:flex;gap:10px;overflow-x:auto;padding:4px 2px 14px;margin-bottom:14px;scrollbar-width:thin}.course-tab{flex:0 0 auto;padding:12px 18px;border:1px solid var(--line);background:#fff;border-radius:13px;font-size:13px;font-weight:800;color:#526177;box-shadow:0 5px 18px rgba(15,23,42,.035);white-space:nowrap}.course-tab:hover{border-color:#bfdbfe;color:var(--brand)}.course-tab.active{background:#eff6ff;border-color:#93c5fd;color:#075bb5}.learning-browser{display:grid;grid-template-columns:290px minmax(0,1fr);gap:18px;align-items:start}.topic-sidebar{background:#fff;border:1px solid var(--line);border-radius:18px;padding:10px;box-shadow:0 7px 25px rgba(15,23,42,.035);position:sticky;top:82px}.topic-head{font-size:12px;font-weight:900;color:#0f172a;padding:10px 12px 13px;border-bottom:1px solid #eef2f7;margin-bottom:7px}.topic-link{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:12px;border-radius:11px;color:#475569;font-size:13px;font-weight:750}.topic-link b{min-width:28px;text-align:center;background:#f1f5f9;color:#64748b;padding:4px 7px;border-radius:999px;font-size:11px}.topic-link:hover{background:#f8fafc;color:var(--brand)}.topic-link.active{background:#eff6ff;color:#075bb5}.topic-link.active b{background:#dbeafe;color:#075bb5}.topic-content{min-height:300px}.topic-title{display:flex;justify-content:space-between;align-items:end;margin-bottom:16px}.topic-title h2{margin:5px 0 0}.topic-count{font-size:12px;font-weight:800;color:#64748b;background:#f8fafc;border:1px solid var(--line);padding:7px 10px;border-radius:999px}.topic-empty,.empty-state{padding:22px 12px;color:#94a3b8;font-size:12px}.empty-state{text-align:center;padding:70px 20px}@media(max-width:800px){.learning-browser{grid-template-columns:1fr}.topic-sidebar{position:static;display:flex;gap:8px;overflow-x:auto}.topic-head{display:none}.topic-link{flex:0 0 auto;border:1px solid var(--line)}.topic-link b{display:none}}
/* 2026-10-07 CLEAN FIX: exam archive uses Year -> Exam -> Problems, not topic tags */
.exam-set-list{display:grid;gap:10px;margin-bottom:22px}.exam-set-card{display:flex;flex-direction:column;gap:5px;padding:14px 16px;border:1px solid #dce6f3;border-radius:14px;text-decoration:none;color:inherit;background:#fff}.exam-set-card:hover,.exam-set-card.active{border-color:#69a9ff;background:#f3f8ff}.exam-set-card span{font-size:13px;color:#64748b}.exam-detail{border-top:1px solid #e5edf7;padding-top:20px;margin-top:8px}

/* Student class leaderboard */
.bm-rank-entry{display:flex;justify-content:flex-end;margin:12px 0}.bm-rank-entry a{padding:11px 16px;background:#eff6ff;border:1px solid #bfdbfe;border-radius:12px;color:#075bb5;font-weight:800;text-decoration:none}
.bm-rank-top{display:flex;justify-content:space-between;gap:12px;margin:20px 0;color:#64748b;font-size:13px}.bm-rank-top a{color:#0b76e0;font-weight:700}.bm-rank-filter{display:flex;align-items:center;gap:12px;flex-wrap:wrap}.bm-rank-filter label{font-weight:800}.bm-rank-filter select{min-width:220px}.bm-my-rank{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;background:#eff6ff;border:1px solid #bfdbfe;border-radius:15px;padding:18px;margin:14px 0 22px;color:#075bb5}.bm-my-rank strong{font-size:20px}.bm-rank-list{display:grid;gap:10px}.bm-rank-row{display:flex;align-items:center;gap:14px;padding:14px;border:1px solid #e2e8f0;border-radius:14px;background:#fff}.bm-rank-row.bm-rank-me{background:#eff6ff;border-color:#60a5fa}.bm-rank-medal{width:48px;height:48px;flex:0 0 48px;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:900;background:#f1f5f9;color:#64748b}.bm-rank-medal span{font-size:30px}.bm-medal-1{background:#fff2bd;color:#d49400}.bm-medal-2{background:#edf0f4;color:#8894a3}.bm-medal-3{background:#f7e2d1;color:#ae6636}.bm-rank-name{flex:1;min-width:0;display:flex;flex-direction:column;gap:4px}.bm-rank-name small,.bm-rank-score small{color:#64748b}.bm-rank-score{display:flex;flex-direction:column;align-items:flex-end;gap:3px}.bm-mvp{font-size:11px;color:#ad7800}.bm-you{font-size:11px;color:#0b76e0;background:#dbeafe;border-radius:6px;padding:3px 6px}@media(max-width:600px){.bm-rank-top span{display:none}.bm-my-rank{flex-direction:column}.bm-rank-score{font-size:12px}}