/* ============================================================
   CAO THANG ETEST — DESIGN SYSTEM v1.4.3
   Quiet, academic, precise. Shared by Student + Admin.
   ============================================================ */
:root {
  --ds-navy-950:#0f2340;
  --ds-navy-900:#17365d;
  --ds-navy-800:#20466f;
  --ds-navy-700:#2b5886;
  --ds-blue-100:#eaf1f8;
  --ds-blue-50:#f4f8fc;
  --ds-gold-600:#a97924;
  --ds-gold-100:#f8f0df;

  --ds-ink-950:#18202b;
  --ds-ink-800:#2d3744;
  --ds-ink-700:#465363;
  --ds-ink-600:#637083;
  --ds-ink-500:#7c8796;
  --ds-line:#dfe5ec;
  --ds-line-soft:#edf1f5;
  --ds-surface:#ffffff;
  --ds-surface-subtle:#f8fafc;
  --ds-canvas:#f3f6f9;

  --ds-success:#23704a;
  --ds-success-bg:#edf7f1;
  --ds-danger:#a33a3a;
  --ds-danger-bg:#fbefef;
  --ds-warning:#8a6118;
  --ds-warning-bg:#fbf5e8;

  --ds-font:-apple-system,BlinkMacSystemFont,"Segoe UI Variable","Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  --ds-font-mono:"SFMono-Regular",Consolas,"Liberation Mono",monospace;

  --ds-text-xs:12px;
  --ds-text-sm:13px;
  --ds-text-md:14px;
  --ds-text-lg:16px;
  --ds-text-xl:18px;
  --ds-text-2xl:22px;
  --ds-text-3xl:28px;
  --ds-text-display:40px;

  --ds-leading-tight:1.25;
  --ds-leading-normal:1.5;
  --ds-leading-relaxed:1.65;

  --ds-space-1:4px;
  --ds-space-2:8px;
  --ds-space-3:12px;
  --ds-space-4:16px;
  --ds-space-5:20px;
  --ds-space-6:24px;
  --ds-space-8:32px;
  --ds-space-10:40px;
  --ds-space-12:48px;
  --ds-space-16:64px;

  --ds-radius-sm:6px;
  --ds-radius-md:10px;
  --ds-radius-lg:14px;
  --ds-radius-xl:18px;
  --ds-shadow-sm:0 1px 2px rgba(15,35,64,.035),0 4px 14px rgba(15,35,64,.045);
  --ds-shadow-md:0 16px 44px rgba(15,35,64,.085);

  --ds-control-h:42px;
  --ds-content:1180px;
  --ds-reading:720px;
}

html{font-size:16px;-webkit-text-size-adjust:100%}
body{font-family:var(--ds-font);font-size:var(--ds-text-md);line-height:var(--ds-leading-normal);color:var(--ds-ink-950);font-weight:400;text-rendering:optimizeLegibility;-webkit-font-smoothing:antialiased}
button,input,select,textarea{font:inherit}
button,a{-webkit-tap-highlight-color:transparent}
::selection{background:#dfeaf6;color:var(--ds-navy-950)}

.ds-eyebrow{font-size:var(--ds-text-xs);line-height:1.3;font-weight:650;letter-spacing:.08em;text-transform:uppercase;color:var(--ds-ink-600)}
.ds-title{font-size:var(--ds-text-3xl);line-height:var(--ds-leading-tight);letter-spacing:-.025em;font-weight:700;color:var(--ds-navy-950)}
.ds-subtitle{font-size:var(--ds-text-md);line-height:var(--ds-leading-relaxed);color:var(--ds-ink-600)}
.ds-muted{color:var(--ds-ink-600)}

.ds-panel{background:var(--ds-surface);border:1px solid var(--ds-line);border-radius:var(--ds-radius-lg);box-shadow:var(--ds-shadow-sm)}
.ds-divider{height:1px;background:var(--ds-line-soft)}

.ds-btn{min-height:var(--ds-control-h);display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:0 18px;border-radius:var(--ds-radius-md);border:1px solid transparent;font-weight:600;font-size:var(--ds-text-md);cursor:pointer;text-decoration:none;transition:background .15s,border-color .15s,color .15s,box-shadow .15s,transform .15s}
.ds-btn:active{transform:translateY(1px)}
.ds-btn-primary{background:var(--ds-navy-900);color:#fff;border-color:var(--ds-navy-900)}
.ds-btn-primary:hover{background:var(--ds-navy-950);border-color:var(--ds-navy-950)}
.ds-btn-secondary{background:#fff;color:var(--ds-navy-900);border-color:var(--ds-line)}
.ds-btn-secondary:hover{border-color:#bdc9d6;background:var(--ds-surface-subtle)}

.ds-input{width:100%;min-height:var(--ds-control-h);padding:9px 12px;border:1px solid var(--ds-line);border-radius:var(--ds-radius-md);background:#fff;color:var(--ds-ink-950);outline:none;transition:border-color .15s,box-shadow .15s}
.ds-input:focus{border-color:#7f9dbb;box-shadow:0 0 0 3px rgba(32,70,111,.09)}

@media(max-width:720px){
  :root{--ds-text-3xl:24px;--ds-text-display:34px;--ds-control-h:44px}
}