/* v6.4 DEV2C · student assignment shell only. Generic practice remains untouched. */
body.v64-student-assignment-exam{background:#f5f7fb}
body.v64-student-assignment-exam .topbar{display:none!important}
body.v64-student-assignment-exam .main-panel{max-width:1120px;margin:0 auto;padding:18px 20px 48px!important}
body.v64-student-assignment-exam #app{min-height:100vh}
body.v64-student-assignment-exam .practice-layout.v64-exam-layout{display:block!important;max-width:900px;margin:0 auto}
body.v64-student-assignment-exam .practice-layout.v64-exam-layout>[data-v64-legacy-side="1"]{display:none!important}
body.v64-student-assignment-exam [data-v64-legacy-progress="1"]{display:none!important}

.v64-exam-head{max-width:900px;margin:0 auto 16px;background:#fff;border:1px solid #e1e7f0;border-radius:24px;padding:20px;box-shadow:0 12px 30px rgba(15,23,42,.06);display:grid;gap:16px}
.v64-exam-head-main{display:flex;align-items:flex-start;justify-content:space-between;gap:16px}
.v64-exam-kicker{display:block;color:#0284c7;font-size:12px;font-weight:900;letter-spacing:.16em;text-transform:uppercase;margin-bottom:7px}
.v64-exam-head h1{margin:0;color:#172033;font-size:25px;line-height:1.25;letter-spacing:-.02em}
.v64-exam-head p{margin:7px 0 0;color:#718096;font-size:13px;font-weight:700}
.v64-exam-head-actions{display:flex;align-items:center;gap:10px;flex:0 0 auto}
.v64-exam-head-actions>button{border:1px solid #d8e1ec;border-radius:13px;background:#f8fafc;color:#475569;font-weight:900;padding:10px 13px;cursor:pointer}
.v64-exam-countdown{display:grid;gap:1px;min-width:108px;padding:8px 12px;border-radius:14px;background:#eff6ff;color:#1d4ed8;text-align:center;border:1px solid #bfdbfe}
.v64-exam-countdown span{font-size:10px;font-weight:800;color:#64748b}
.v64-exam-countdown b{font-size:20px;line-height:1.1;font-variant-numeric:tabular-nums;letter-spacing:.03em}
.v64-exam-countdown.danger{background:#fff1f2;border-color:#fecdd3;color:#be123c}

.v64-exam-progress{display:grid;gap:7px}
.v64-exam-progress>div:first-child{display:flex;justify-content:space-between;align-items:center;gap:12px;color:#334155}
.v64-exam-progress>div:first-child b{font-size:14px}.v64-exam-progress>div:first-child span{font-size:12px;color:#718096;font-weight:800}
.v64-exam-progress>div:last-child{height:7px;border-radius:999px;background:#e9eef5;overflow:hidden}
.v64-exam-progress i{display:block;height:100%;border-radius:inherit;background:linear-gradient(90deg,#2563eb,#06b6d4)}

.v64-exam-navigator{border-top:1px solid #edf1f6;padding-top:14px;display:grid;gap:10px}
.v64-exam-filter-row{display:grid;grid-template-columns:1fr 1fr auto;gap:10px;align-items:end}
.v64-exam-filter-row label{display:grid;gap:5px;min-width:0}
.v64-exam-filter-row label span{font-size:11px;color:#64748b;font-weight:900}
.v64-exam-filter-row select{width:100%;min-width:0;border:1px solid #d8e1ec;background:#fff;color:#26364b;border-radius:12px;padding:10px 34px 10px 11px;font:inherit;font-size:13px;font-weight:800;outline:none}
.v64-exam-filter-row select:focus{border-color:#60a5fa;box-shadow:0 0 0 3px rgba(59,130,246,.1)}
.v64-exam-nav-toggle{border:1px solid #d8e1ec;border-radius:12px;background:#f8fafc;color:#334155;font-weight:900;padding:10px 12px;white-space:nowrap;cursor:pointer}
.v64-exam-nav-toggle b{margin-left:4px;color:#0284c7}.v64-exam-nav-toggle.on{background:#eff6ff;border-color:#bfdbfe;color:#1d4ed8}
.v64-exam-number-panel{display:none;border:1px solid #e2e8f0;background:#f8fafc;border-radius:15px;padding:10px;max-height:240px;overflow:auto}
.v64-exam-number-panel.open{display:block}
.v64-exam-number-panel>div{display:grid;grid-template-columns:repeat(auto-fill,minmax(42px,1fr));gap:7px}
.v64-exam-number-panel button{height:40px;border:1px solid #d7e0eb;border-radius:10px;background:#fff;color:#475569;font-weight:900;cursor:pointer}
.v64-exam-number-panel button.current{background:#2563eb;border-color:#2563eb;color:#fff;box-shadow:0 4px 10px rgba(37,99,235,.22)}
.v64-exam-number-panel button.done:not(.current){background:#ecfdf5;border-color:#a7f3d0;color:#047857}
.v64-exam-number-panel button.wrong:not(.current){background:#fff1f2;border-color:#fecdd3;color:#be123c}

body.v64-student-assignment-exam .question-card{border:1px solid #e1e7f0!important;border-radius:24px!important;background:#fff!important;box-shadow:0 12px 30px rgba(15,23,42,.055)!important;padding:22px!important;overflow:hidden}
body.v64-student-assignment-exam .question-top{margin-bottom:13px!important;display:flex!important;gap:7px!important;align-items:center!important}
body.v64-student-assignment-exam .question-top .badge:not(.v64-keep-type){display:none!important}
body.v64-student-assignment-exam .question-top .v64-keep-type{background:#eaf6ff!important;color:#0369a1!important;border:0!important;font-size:12px!important;padding:6px 9px!important}
body.v64-student-assignment-exam .batch-tip,
body.v64-student-assignment-exam .instant-tip,
body.v64-student-assignment-exam .instant-lock-note{display:none!important}
body.v64-student-assignment-exam .question-text,
body.v64-student-assignment-exam .stem-title{font-size:19px!important;line-height:1.75!important;color:#172033!important;font-weight:750!important;margin:8px 0 18px!important}
body.v64-student-assignment-exam .material-reading-box{border-radius:16px!important;background:#f8fafc!important;border:1px solid #e2e8f0!important;padding:15px!important;margin-bottom:14px!important}
body.v64-student-assignment-exam .options{display:grid!important;gap:10px!important}
body.v64-student-assignment-exam .option{border:1px solid #dce4ed!important;border-radius:16px!important;background:#fff!important;min-height:58px!important;padding:13px 14px!important;box-shadow:none!important;transition:border-color .15s ease,background .15s ease,transform .15s ease!important}
body.v64-student-assignment-exam .option:hover{border-color:#93c5fd!important;background:#f8fbff!important}
body.v64-student-assignment-exam .option.selected{border-color:#60a5fa!important;background:#eff6ff!important}
body.v64-student-assignment-exam .answer-panel{border-radius:16px!important;margin-top:14px!important}
body.v64-student-assignment-exam .footer-tools{margin-top:20px!important;padding-top:16px!important;border-top:1px solid #edf1f6!important;display:grid!important;gap:10px!important}
body.v64-student-assignment-exam .footer-tools>.actions:first-child{display:grid!important;grid-template-columns:minmax(82px,1fr) minmax(110px,1.3fr) minmax(82px,1fr)!important;gap:9px!important}
body.v64-student-assignment-exam .footer-tools>.actions:first-child .btn{width:100%!important;min-width:0!important;margin:0!important;border-radius:13px!important;padding:12px 8px!important;font-weight:900!important}
body.v64-student-assignment-exam .footer-tools>.actions:nth-child(2){display:flex!important;justify-content:flex-end!important;gap:8px!important}
body.v64-student-assignment-exam .footer-tools>.actions:nth-child(2) #quitBtn{display:none!important}
body.v64-student-assignment-exam .footer-tools>.actions:nth-child(2) .btn{font-size:12px!important;padding:8px 11px!important;border-radius:11px!important}

/* DEV2A/DEV2B overlay navigation is superseded by the dedicated DEV2C shell. */
body.v64-student-assignment-exam .v64-student-practice-nav{display:none!important}
body.v64-student-assignment-exam .v64-assignment-nav-hidden{display:inline-flex!important}

@media(max-width:720px){
  body.v64-student-assignment-exam .main-panel{padding:10px 10px 34px!important}
  .v64-exam-head{border-radius:20px;padding:15px;margin-bottom:10px;gap:13px}
  .v64-exam-head-main{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:10px}
  .v64-exam-head h1{font-size:21px;line-height:1.3}
  .v64-exam-head p{font-size:12px;margin-top:5px}
  .v64-exam-kicker{font-size:10px;margin-bottom:5px}
  .v64-exam-head-actions{display:grid;gap:7px;justify-items:stretch}
  .v64-exam-countdown{min-width:91px;padding:7px 9px;border-radius:12px}.v64-exam-countdown b{font-size:17px}
  .v64-exam-head-actions>button{padding:8px 10px;font-size:12px}
  .v64-exam-filter-row{grid-template-columns:1fr 1fr;gap:8px}
  .v64-exam-nav-toggle{grid-column:1/-1;width:100%}
  .v64-exam-number-panel{max-height:210px;padding:8px}
  .v64-exam-number-panel>div{grid-template-columns:repeat(6,minmax(0,1fr));gap:6px}.v64-exam-number-panel button{height:38px;font-size:12px}
  body.v64-student-assignment-exam .question-card{border-radius:20px!important;padding:16px!important}
  body.v64-student-assignment-exam .question-text,body.v64-student-assignment-exam .stem-title{font-size:17px!important;line-height:1.72!important}
  body.v64-student-assignment-exam .option{min-height:54px!important;border-radius:14px!important;padding:12px!important}
  body.v64-student-assignment-exam .footer-tools>.actions:first-child{grid-template-columns:1fr 1.25fr 1fr!important;gap:7px!important}
  body.v64-student-assignment-exam .footer-tools>.actions:first-child .btn{font-size:13px!important;padding:11px 5px!important}
}
@media(max-width:390px){
  .v64-exam-head-main{grid-template-columns:1fr}.v64-exam-head-actions{display:flex;justify-content:space-between}.v64-exam-countdown{flex:1}.v64-exam-head-actions>button{align-self:stretch}
  .v64-exam-filter-row{grid-template-columns:1fr}.v64-exam-nav-toggle{grid-column:auto}
  .v64-exam-number-panel>div{grid-template-columns:repeat(5,minmax(0,1fr))}
  body.v64-student-assignment-exam .footer-tools>.actions:first-child{grid-template-columns:1fr 1fr!important}
  body.v64-student-assignment-exam .footer-tools>.actions:first-child #submitBtn,body.v64-student-assignment-exam .footer-tools>.actions:first-child #finishBtn{grid-column:1/-1;grid-row:1}
}
@media(prefers-color-scheme:dark){
  body.v64-student-assignment-exam{background:#090f1b}.v64-exam-head,body.v64-student-assignment-exam .question-card{background:#0f172a!important;border-color:#263449!important;color:#e5e7eb!important}
  .v64-exam-head h1,body.v64-student-assignment-exam .question-text,body.v64-student-assignment-exam .stem-title{color:#f1f5f9!important}.v64-exam-head p,.v64-exam-progress>div:first-child span{color:#94a3b8}
  .v64-exam-navigator{border-color:#263449}.v64-exam-filter-row select,.v64-exam-nav-toggle,.v64-exam-number-panel,.v64-exam-number-panel button{background:#111827;border-color:#334155;color:#dbeafe}.v64-exam-number-panel button.current{background:#2563eb;border-color:#2563eb;color:#fff}
  body.v64-student-assignment-exam .option{background:#111827!important;border-color:#334155!important;color:#e5e7eb!important}.v64-exam-progress>div:last-child{background:#263449}
}