:root{
    --bg:#f4f6fb; --panel:#ffffff; --ink:#1f2a44; --muted:#7a86a1;
    --line:#e6eaf2; --brand:#3a6df0; --brand2:#22b07d; --warn:#f0883e;
    --shadow:0 4px 18px rgba(31,42,68,.08);
}
*{box-sizing:border-box;margin:0;padding:0}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
    background:var(--bg);color:var(--ink);font-size:14px;line-height:1.6}
a{color:inherit;text-decoration:none}
button,input,select,textarea{font-family:inherit;font-size:14px}

.app{display:flex;min-height:100vh}
/* 侧边栏 */
.sidebar{width:230px;background:#11182e;color:#cdd5ea;display:flex;flex-direction:column;
    position:fixed;height:100vh;padding:18px 12px}
.brand{display:flex;align-items:center;gap:10px;padding:6px 8px 18px}
.logo{width:40px;height:40px;border-radius:11px;background:linear-gradient(135deg,var(--brand),var(--brand2));
    display:flex;align-items:center;justify-content:center;font-size:20px;color:#fff;font-weight:700}
.brand-title{font-weight:700;color:#fff;font-size:15px}
.brand-sub{font-size:11px;color:#7e8aa8}
#nav{display:flex;flex-direction:column;gap:4px;margin-top:8px}
.nav-item{padding:10px 12px;border-radius:9px;color:#aeb8d4;cursor:pointer;display:flex;align-items:center;gap:9px;transition:.15s}
.nav-item:hover{background:#1c2742;color:#fff}
.nav-item.active{background:var(--brand);color:#fff}
.ico{font-size:16px}
.sidebar-foot{margin-top:auto;font-size:11px;color:#5e688a;padding:10px 8px}

/* 主区 */
.main{margin-left:230px;flex:1;padding:26px 32px;max-width:1100px}
.page-head{margin-bottom:18px}
.page-head h1{font-size:22px;font-weight:700}
.muted{color:var(--muted);font-size:13px;margin-top:2px}

/* 卡片 */
.card{background:var(--panel);border:1px solid var(--line);border-radius:14px;
    padding:18px;margin-bottom:18px;box-shadow:var(--shadow)}
.card h3{font-size:15px;margin-bottom:12px}
.card h3:not(:first-child){margin-top:6px}

/* 概览 */
.stat-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:14px;margin-bottom:18px}
.stat{background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:16px;box-shadow:var(--shadow)}
.stat .num{font-size:26px;font-weight:700;color:var(--brand)}
.stat .lab{color:var(--muted);font-size:13px;margin-top:2px}
.recent-list .ri{display:flex;justify-content:space-between;padding:9px 0;border-bottom:1px dashed var(--line);font-size:13px}
.recent-list .ri:last-child{border-bottom:none}

/* 表单 */
.row-form{display:flex;gap:10px;flex-wrap:wrap}
.grid-form{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.grid-form label{display:flex;flex-direction:column;gap:5px;font-size:13px;color:var(--muted)}
.grid-form label.full{grid-column:1/3}
input[type=text],input[type=number],input[type=date],select,textarea{
    border:1px solid var(--line);border-radius:9px;padding:9px 11px;background:#fbfcfe;color:var(--ink);width:100%}
textarea{resize:vertical}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--brand);background:#fff}

.btn{border:1px solid var(--line);background:#fff;color:var(--ink);padding:9px 14px;border-radius:9px;
    cursor:pointer;transition:.15s;font-weight:500;white-space:nowrap}
.btn:hover{border-color:var(--brand);color:var(--brand)}
.btn.primary{background:var(--brand);color:#fff;border-color:var(--br)}
.btn.primary:hover{background:#2f5bd0;color:#fff}
.btn.ghost{background:transparent}
.btn.danger{color:#e0584b;border-color:#f1c4bf}
.btn.danger:hover{background:#fdeceb;color:#e0584b}
.btn.sm{padding:5px 10px;font-size:12px}

.toolbar{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.check-group{display:flex;flex-wrap:wrap;gap:8px}
.check-group label{display:flex;align-items:center;gap:5px;background:#f7f9fd;border:1px solid var(--line);
    padding:6px 10px;border-radius:20px;color:var(--ink);cursor:pointer}
.two-col{display:grid;grid-template-columns:1fr 1fr;gap:18px}
.mastered-row{display:flex;gap:8px;margin-bottom:8px}
.mastered-row .m-content{flex:1}
.mastered-row .m-percent{width:90px}

/* 表格 */
.tbl{width:100%;border-collapse:collapse;font-size:13px}
.tbl th,.tbl td{padding:10px 8px;text-align:left;border-bottom:1px solid var(--line);vertical-align:middle}
.tbl th{color:var(--muted);font-weight:600;background:#fafbfe}
.tbl tr:hover td{background:#fafcff}
.tag{display:inline-block;padding:2px 9px;border-radius:20px;font-size:12px;font-weight:600}
.tag.teacher{background:#e8f0ff;color:var(--brand)}
.tag.student{background:#e6f7ef;color:var(--brand2)}
.tag.ok{background:#e6f7ef;color:var(--brand2)}
.link{color:var(--brand);cursor:pointer;text-decoration:underline}
.bar{height:7px;background:#eef1f7;border-radius:5px;overflow:hidden;min-width:70px}
.bar>i{display:block;height:100%;background:linear-gradient(90deg,var(--brand),var(--brand2))}

/* 记录列表（课堂/作业） */
.record-list .rec{border:1px solid var(--line);border-radius:12px;padding:14px;margin-bottom:12px;background:#fbfcfe}
.rec h4{font-size:14px;margin-bottom:6px;display:flex;justify-content:space-between}
.rec .meta{color:var(--muted);font-size:12px;margin-bottom:6px}
.rec .body{font-size:13px;white-space:pre-wrap}
.rec .kp{background:#fff8ef;border-left:3px solid var(--warn);padding:8px 10px;border-radius:6px;margin-top:8px;font-size:13px}
.rec .actions{margin-top:10px;display:flex;gap:8px}

/* 弹窗 */
.modal{display:none;position:fixed;inset:0;background:rgba(10,15,30,.8);z-index:99;
    align-items:center;justify-content:center;padding:40px}
.modal.show{display:flex}
.modal img{max-width:90%;max-height:90%;border-radius:8px;background:#fff}
.modal-close{position:absolute;top:20px;right:30px;font-size:34px;color:#fff;cursor:pointer}

/* 登录 */
.login-overlay{display:none;position:fixed;inset:0;background:#11182e;z-index:200;
    align-items:center;justify-content:center}
.login-overlay.show{display:flex}
.login-box{background:#fff;border-radius:16px;padding:26px;width:320px;box-shadow:var(--shadow)}
.login-box input{margin:14px 0;width:100%}
.login-err{color:#e0584b;font-size:13px;min-height:18px;text-align:center;margin-top:6px}
.sidebar-foot .link{color:#9fb0d8;font-size:12px}
.sidebar-foot .link:hover{color:#fff}

/* 登录标签切换 */
.login-tabs{display:flex;gap:6px;margin-bottom:14px}
.ltab{flex:1;padding:8px;border:1px solid var(--line);background:#f7f9fd;border-radius:9px;cursor:pointer;color:var(--muted);font-size:13px}
.ltab.active{background:var(--brand);color:#fff;border-color:var(--brand)}
.login-box input{margin:8px 0;width:100%}
.login-err{color:#e0584b;font-size:13px;min-height:18px;text-align:center;margin-top:6px}
code.code{background:#f1f4fb;padding:2px 8px;border-radius:6px;font-family:ui-monospace,monospace;letter-spacing:1px}

@media(max-width:880px){
    .sidebar{width:100%;height:auto;position:relative;flex-direction:row;flex-wrap:wrap;align-items:center}
    #nav{flex-direction:row;flex-wrap:wrap;width:100%}
    .sidebar-foot{display:none}
    .main{margin-left:0;padding:16px}
    .stat-grid{grid-template-columns:repeat(2,1fr)}
    .grid-form,.two-col{grid-template-columns:1fr}
    .grid-form label.full{grid-column:auto}
}