:root{
  --bg:#f4f6fa; --panel:#ffffff; --border:#d9dee7;
  --text:#2b323c; --muted:#7b8595; --brand:#3a6ee8;
  --brand-d:#2b55c0; --green:#28a06b; --warn:#e8a13a; --danger:#e05252;
  --header:#fff7d6; --header2:#fff2c2; --date:#fdeecf; --day:#f9fbff;
  --shadow:0 2px 10px rgba(40,60,90,.08);
}
*{box-sizing:border-box}
html,body{height:100%;margin:0}
body{font-family:"Segoe UI","Microsoft YaHei",system-ui,sans-serif;color:var(--text);background:var(--bg);font-size:14px}
.hidden{display:none!important}
button{font-family:inherit}

/* login */
.login-view{min-height:100vh;display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,#eef2ff 0%,#f6f9ff 100%)}
.login-card{background:var(--panel);padding:36px 40px;border-radius:16px;box-shadow:var(--shadow);width:380px;text-align:center}
.login-logo{display:flex;justify-content:center;margin-bottom:6px}
.login-card h1{margin:10px 0 2px;font-size:22px}
.login-sub{color:var(--muted);margin:0 0 24px}
.field{margin-bottom:16px;text-align:left}
.field label{display:block;margin-bottom:6px;color:var(--muted);font-size:13px}
.field input{width:100%;padding:11px 12px;border:1px solid var(--border);border-radius:8px;font-size:14px;outline:none}
.field input:focus{border-color:var(--brand)}
.login-msg{margin-top:14px;min-height:20px;color:var(--danger);font-size:13px}

/* buttons */
.btn{border:1px solid var(--border);background:#fff;color:var(--text);padding:8px 14px;border-radius:8px;cursor:pointer;font-size:13px;transition:.15s;white-space:nowrap}
.btn:hover{background:#f0f3f8}
.btn:disabled{opacity:.5;cursor:not-allowed}
.btn-primary{background:var(--brand);color:#fff;border-color:var(--brand)}
.btn-primary:hover{background:var(--brand-d)}
.btn-warn{background:var(--warn);color:#fff;border-color:var(--warn)}
.btn-danger{background:var(--danger);color:#fff;border-color:var(--danger)}
.btn-ghost{background:transparent;border-color:transparent;color:var(--muted)}
.btn-ghost:hover{color:var(--text);background:#eef1f6}
.btn-block{width:100%;display:block;margin-bottom:8px}
.btn-sm{padding:5px 10px;font-size:12px}

/* app layout */
.app-view{display:flex;flex-direction:column;height:100vh}
.topbar{display:flex;align-items:center;gap:16px;background:var(--panel);border-bottom:1px solid var(--border);padding:0 16px;height:54px;flex-shrink:0}
.topbar-title{display:flex;align-items:center;gap:10px;font-weight:600}
.topbar-title .logo{display:flex;align-items:center}
.topbar-title .brand-text{display:flex;flex-direction:column;line-height:1.06;margin-right:6px}
.topbar-title .title{font-size:17px;font-weight:800;color:#1a1a1a;letter-spacing:.5px;white-space:nowrap}
.topbar-title .subtitle{font-size:9px;color:#9aa4b2;letter-spacing:2px;text-transform:uppercase;white-space:nowrap}
.topbar-actions{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.topbar-right{margin-left:auto;display:flex;align-items:center;gap:8px}
.user-name{font-weight:600;margin-right:4px}

.badge{background:#eef1f6;padding:3px 10px;border-radius:20px;font-size:12px;color:var(--muted)}
.status-badge{background:var(--header);padding:3px 10px;border-radius:20px;font-size:12px;font-weight:600;color:#8a6d00}

.main{display:flex;flex:1;overflow:hidden}
.sidebar{width:300px;background:var(--panel);border-right:1px solid var(--border);display:flex;flex-direction:column;flex-shrink:0}
.sidebar-head{display:flex;justify-content:space-between;align-items:center;padding:12px 14px;border-bottom:1px solid var(--border);font-weight:600}
.turn-indicator{font-size:12px;color:var(--brand);font-weight:600}
.student-roster{flex:1;overflow:auto;padding:6px 0}
.student-row{display:flex;align-items:center;gap:10px;padding:8px 14px;cursor:default}
.student-row.active{background:#eaf1ff}
.student-row .seq{width:28px;height:28px;border-radius:50%;background:#eef1f6;display:flex;align-items:center;justify-content:center;font-weight:600;font-size:13px;flex-shrink:0}
.student-row.active .seq{background:var(--brand);color:#fff}
.student-row .nm{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.student-row .tag{font-size:11px;color:var(--green);font-weight:600}
.instructor-manage{border-top:1px solid var(--border);padding:12px 14px}
.manage-title{font-weight:600;margin-bottom:10px;color:var(--muted);font-size:12px}

/* board */
.board{flex:1;display:flex;flex-direction:column;overflow:hidden;position:relative}
.student-banner{background:linear-gradient(90deg,#eaf1ff,#f4f8ff);border-bottom:1px solid var(--border);padding:8px 16px;display:flex;align-items:center;gap:14px;flex-wrap:wrap}
.student-banner .msg{font-weight:600}
.countdown{font-variant-numeric:tabular-nums;font-weight:700;color:var(--brand);font-size:18px}
.sheet-wrap{flex:1;display:flex;flex-direction:column;overflow:hidden;padding:10px}
.sheet-scroll{flex:1;overflow:auto;border:1px solid var(--border);border-radius:8px;background:#fff}
.day-tabs{display:flex;gap:4px;padding:8px 2px 0;overflow-x:auto;flex-shrink:0}
.day-tab{padding:7px 14px;border:1px solid var(--border);background:#f0f3f8;border-radius:8px 8px 0 0;cursor:pointer;font-size:13px;white-space:nowrap;border-bottom:none}
.day-tab.active{background:#fff;color:var(--brand);font-weight:600;border-top:3px solid var(--brand)}

/* sheet */
.sheet{border-collapse:collapse;width:100%;table-layout:fixed;font-size:12px}
.sheet th,.sheet td{border-right:1px solid var(--border);border-bottom:1px solid var(--border);padding:0;vertical-align:middle;text-align:center;height:44px;overflow:hidden}
.sheet thead th{position:sticky;top:0;background:var(--header);color:#7a5c00;font-weight:600;z-index:3;height:34px;padding:2px 4px}
.sheet thead th.slot{font-size:11px}
.sheet th.slot.g1{background:#fff3c4}
.sheet th.slot.g2{background:#ffe9c2}
.sheet th.slot .gname{display:block;font-size:10px;color:#a0721a;margin-bottom:2px}
.sheet th.corner{left:0;top:0;z-index:5;background:var(--date)}
.sheet th.corner,.sheet td.label{position:sticky;left:0;z-index:2;font-weight:600;color:#7a5210}
.sheet td.rack-label{position:sticky;left:0;z-index:2;background:var(--date);font-weight:600;text-align:left;padding:0 10px;color:#7a5210}
.sheet td.rack-label .rack-type{font-size:10px;color:#b08a3a;font-weight:400;margin-top:2px}
.sheet td.date-label{position:sticky;left:0;z-index:2;background:var(--date);font-weight:700;color:#7a5210}
.sheet td.date-label .wd{font-size:14px}
.sheet td.date-label .dt{font-size:10px;color:#b08a3a;font-weight:400;margin-top:2px}
.sheet td.region{position:sticky;left:120px;z-index:2}
.sheet td.region{background:#fdf5e7;font-weight:700;color:#8a6d00;width:52px}
.sheet td.cell{cursor:pointer;position:relative}
.sheet td.cell.empty{background:#fff}
.sheet td.cell.empty:hover{background:#eef4ff}
.sheet td.cell.none{cursor:default;background:#f6f7f9}
.sheet td.cell.taken{background:#eafbe7;color:#276b3c}
.sheet td.cell.taken.other{background:#eef1f6;color:#667}
.sheet td.cell.taken .nm{display:block;overflow:hidden;white-space:nowrap;font-size:12px;padding:0 4px}
.sheet td.cell .mark{position:absolute;top:2px;right:4px;font-size:10px;color:var(--danger)}
.sheet td.cell.locked{cursor:default}
.sheet.locked td.cell.empty:hover{background:#fff}
.sheet th:nth-child(n+3),.sheet td:nth-child(n+3){width:92px}
.sheet .slotnum{font-size:10px;color:#a0855a;display:block;margin-top:-4px}

/* room allocation colors per student (hash -> palette) */
.sheet td.cell.col-0{background:#eafbe7}
.sheet td.cell.col-1{background:#e8f0ff}
.sheet td.cell.col-2{background:#f6e8ff}
.sheet td.cell.col-3{background:#fff3e0}
.sheet td.cell.col-4{background:#e6f7ff}
.sheet td.cell.col-5{background:#fdeef0}
.sheet td.cell.col-6{background:#eef9ea}
.sheet td.cell.col-7{background:#f0f0ff}
.sheet td.cell.col-8{background:#f7f3ff}
.sheet td.cell.col-name{background:#fdf3e3}
.day-tab .tab-type{font-size:10px;color:#b08a3a;margin-left:5px;font-weight:400}

/* modal */
.modal-mask{position:fixed;inset:0;background:rgba(20,30,50,.45);display:flex;align-items:center;justify-content:center;z-index:100}
.modal{background:#fff;border-radius:14px;box-shadow:0 10px 40px rgba(0,0,0,.2);width:min(720px,94vw);max-height:88vh;display:flex;flex-direction:column}
.modal-head{padding:16px 20px;border-bottom:1px solid var(--border);display:flex;justify-content:space-between;align-items:center;font-weight:600}
.modal-close{cursor:pointer;border:none;background:none;font-size:22px;color:var(--muted)}
.modal-body{padding:16px 20px;overflow:auto}
.modal-foot{padding:12px 20px;border-top:1px solid var(--border);display:flex;justify-content:flex-end;gap:8px}
.modal h4{margin:14px 0 8px;color:var(--muted);font-size:13px}

/* tables in modals */
.tbl{width:100%;border-collapse:collapse;font-size:13px}
.tbl th,.tbl td{border:1px solid var(--border);padding:7px 10px;text-align:left}
.tbl th{background:#f6f8fb}
.tbl .actions{display:flex;gap:6px}

/* forms */
.form-row{display:flex;gap:12px;margin-bottom:12px;align-items:flex-end;flex-wrap:wrap}
.form-item{display:flex;flex-direction:column;gap:5px}
.form-item label{font-size:12px;color:var(--muted)}
.form-item input,.form-item select{border:1px solid var(--border);border-radius:8px;padding:8px 10px;font-size:13px;outline:none;min-width:110px}
.form-item input:focus{border-color:var(--brand)}
.form-item-wide{min-width:100%}
.chklist{display:flex;flex-wrap:wrap;gap:6px 16px;max-width:520px}
.chklist .chk{display:inline-flex;align-items:center;gap:4px;font-size:13px;cursor:pointer;padding:2px 4px}
.chklist .chk:hover{color:var(--brand)}

/* toast */
.toast-root{position:fixed;top:70px;left:50%;transform:translateX(-50%);z-index:300;display:flex;flex-direction:column;gap:8px;align-items:center}
.toast{background:#2b323c;color:#fff;padding:10px 18px;border-radius:10px;box-shadow:var(--shadow);font-size:13px;animation:fadein .2s}
.toast.error{background:#d64848}
.toast.success{background:#2b8d58}
@keyframes fadein{from{opacity:0;transform:translateY(-6px)}to{opacity:1;transform:none}}

.empty-hint{color:var(--muted);text-align:center;padding:24px}
.admin-panel{flex:1;overflow:auto;padding:24px;background:var(--bg)}
.admin-panel h2{margin:0 0 16px}
.admin-panel .tbl{margin-bottom:8px}
.note{color:var(--muted);font-size:12px;margin-top:10px;line-height:1.6}
.mini{border:1px solid var(--border);border-radius:6px;padding:5px 7px;font-size:13px;outline:none}
.mini:focus{border-color:var(--brand)}

/* link box */
.linkbox{display:flex;gap:8px;align-items:center}
.linkbox input{flex:1;padding:8px;border:1px solid var(--border);border-radius:8px;font-size:12px}

@media (max-width:1000px){
  .sidebar{width:240px}
}