:root{
  --primary:#2563eb; --primary-dark:#1d4ed8; --success:#16a34a; --danger:#dc2626;
  --bg:#f5f7fb; --card:#ffffff; --border:#e2e8f0; --text:#1e293b; --muted:#64748b;
}
*{box-sizing:border-box;}
body{margin:0;font-family:'Sarabun',-apple-system,Segoe UI,Arial,sans-serif;background:var(--bg);color:var(--text);}
.container{max-width:1100px;margin:0 auto;padding:0 20px;}
a{color:var(--primary);text-decoration:none;}
a:hover{text-decoration:underline;}

.site-header{background:var(--card);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:10;}
.header-inner{display:flex;justify-content:space-between;align-items:center;height:64px;}
.logo{font-weight:700;font-size:20px;color:var(--text);}
.logo span{color:var(--primary);}
.header-inner nav{display:flex;align-items:center;gap:16px;}
.user-name{color:var(--muted);}
.btn-primary-sm{background:var(--primary);color:#fff;padding:8px 16px;border-radius:8px;}
.btn-primary-sm:hover{background:var(--primary-dark);text-decoration:none;color:#fff;}

.main-content{padding:32px 20px;min-height:70vh;}

.alert{padding:12px 16px;border-radius:8px;margin-bottom:20px;}
.alert-error{background:#fef2f2;color:var(--danger);border:1px solid #fecaca;}
.alert-success{background:#f0fdf4;color:var(--success);border:1px solid #bbf7d0;}

.card{background:var(--card);border:1px solid var(--border);border-radius:12px;padding:24px;margin-bottom:20px;}
.exam-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:20px;}
.exam-card h3{margin:0 0 8px;}
.exam-card .meta{color:var(--muted);font-size:14px;margin-bottom:12px;}
.badge{display:inline-block;padding:2px 10px;border-radius:999px;font-size:12px;font-weight:600;}
.badge-free{background:#f0fdf4;color:var(--success);}
.badge-paid{background:#fff7ed;color:#c2410c;}

.btn{display:inline-block;background:var(--primary);color:#fff;border:none;padding:10px 20px;border-radius:8px;cursor:pointer;font-size:15px;}
.btn:hover{background:var(--primary-dark);text-decoration:none;color:#fff;}
.btn-outline{background:transparent;border:1px solid var(--primary);color:var(--primary);}
.btn-danger{background:var(--danger);}
.btn-block{display:block;width:100%;text-align:center;}

form.auth-form{max-width:420px;margin:0 auto;}
.form-group{margin-bottom:16px;}
label{display:block;margin-bottom:6px;font-weight:600;font-size:14px;}
input[type=text],input[type=email],input[type=password],input[type=number],textarea,select{
  width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:8px;font-size:15px;font-family:inherit;
}
textarea{resize:vertical;}

table{width:100%;border-collapse:collapse;}
table th,table td{padding:10px 12px;border-bottom:1px solid var(--border);text-align:left;font-size:14px;}
table th{background:#f8fafc;}

.timer-box{position:sticky;top:74px;background:#111827;color:#fff;padding:12px 20px;border-radius:10px;text-align:center;font-size:22px;font-weight:700;margin-bottom:20px;z-index:5;}
.timer-box.warning{background:var(--danger);}

.question-block{padding:20px 0;border-bottom:1px solid var(--border);}
.question-block:last-child{border-bottom:none;}
.question-text{font-weight:600;margin-bottom:12px;}
.option-row{display:flex;align-items:flex-start;gap:10px;padding:8px 12px;border:1px solid var(--border);border-radius:8px;margin-bottom:8px;cursor:pointer;}
.option-row:hover{background:#f8fafc;}
.option-row input{margin-top:3px;}

.score-circle{width:160px;height:160px;border-radius:50%;display:flex;align-items:center;justify-content:center;flex-direction:column;margin:0 auto 20px;border:8px solid var(--primary);}
.score-circle.passed{border-color:var(--success);}
.score-circle.failed{border-color:var(--danger);}
.score-circle .num{font-size:36px;font-weight:700;}

.site-footer{padding:24px 0;text-align:center;color:var(--muted);font-size:14px;}

.admin-layout{display:flex;min-height:100vh;}
.admin-sidebar{width:230px;background:#111827;color:#fff;flex-shrink:0;}
.admin-sidebar a{display:block;color:#cbd5e1;padding:12px 20px;}
.admin-sidebar a:hover,.admin-sidebar a.active{background:#1f2937;color:#fff;text-decoration:none;}
.admin-sidebar .brand{padding:20px;font-weight:700;font-size:18px;color:#fff;border-bottom:1px solid #1f2937;}
.admin-content{flex:1;padding:28px;}
.stats-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:16px;margin-bottom:24px;}
.stat-box{background:#fff;border:1px solid var(--border);border-radius:12px;padding:18px;}
.stat-box .num{font-size:28px;font-weight:700;}
.stat-box .label{color:var(--muted);font-size:13px;}
.toolbar{display:flex;justify-content:space-between;align-items:center;margin-bottom:16px;}