/* ========== K12 Learning OS App · Style ========== */
:root {
    --bg-0:#0b0f1e; --bg-1:#131a2e;
    --bg-card:rgba(255,255,255,0.04);
    --bg-card-h:rgba(255,255,255,0.08);
    --border:rgba(255,255,255,0.09);
    --text-0:#e8ecf5; --text-1:#b6bfd0; --text-2:#7c8699;
    --accent:#7c5cff; --accent-2:#22d3ee; --accent-3:#f472b6;
    --success:#34d399; --warn:#fbbf24; --danger:#f87171;
    --radius:14px;
    --sidebar-w:220px;
    --shadow:0 8px 32px rgba(0,0,0,0.35);
}
*{margin:0;padding:0;box-sizing:border-box}
html,body{min-height:100%}
html{background:var(--bg-0)}
body{
    font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
    background:radial-gradient(ellipse at top,#1a2245 0%,var(--bg-0) 55%) fixed;
    color:var(--text-0);line-height:1.6;-webkit-font-smoothing:antialiased;
}
a{color:var(--accent-2);text-decoration:none}
button{font-family:inherit;cursor:pointer}
[x-cloak]{display:none!important}

/* ========== Layout ========== */
.app{display:flex;min-height:100vh}
.sidebar{
    width:var(--sidebar-w);flex-shrink:0;
    background:rgba(0,0,0,0.25);border-right:1px solid var(--border);
    padding:20px 0;position:fixed;top:0;bottom:0;left:0;overflow-y:auto;
}
.sidebar .brand{padding:0 20px 18px;border-bottom:1px solid var(--border);margin-bottom:14px}
.sidebar .brand h1{font-size:16px;font-weight:700;letter-spacing:1px}
.sidebar .brand .sub{font-size:11px;color:var(--text-2);letter-spacing:2px;margin-top:2px}
.sidebar .nav-item{
    display:flex;align-items:center;gap:10px;
    padding:10px 20px;color:var(--text-1);font-size:14px;
    cursor:pointer;border-left:3px solid transparent;transition:all .15s;
}
.sidebar .nav-item:hover{background:var(--bg-card-h);color:var(--text-0)}
.sidebar .nav-item.active{
    background:linear-gradient(90deg,rgba(124,92,255,0.15),transparent);
    color:var(--text-0);border-left-color:var(--accent);
}
.sidebar .nav-item .icon{font-size:18px;flex-shrink:0}
.sidebar .foot{padding:20px;font-size:11px;color:var(--text-2);border-top:1px solid var(--border);margin-top:20px}

.main{flex:1;margin-left:var(--sidebar-w);padding:30px 40px;max-width:1400px}

/* ========== Cards & Common ========== */
.card{
    background:var(--bg-card);border:1px solid var(--border);
    border-radius:var(--radius);padding:20px;margin-bottom:18px;
}
.card h2{font-size:18px;font-weight:600;margin-bottom:12px}
.card h3{font-size:15px;color:var(--accent-2);margin:14px 0 8px}
.card p{color:var(--text-1);margin-bottom:8px;font-size:14px}
.badge{display:inline-block;padding:2px 10px;border-radius:100px;font-size:11px;letter-spacing:1px;
    background:rgba(124,92,255,0.15);border:1px solid rgba(124,92,255,0.3);color:var(--accent)}
.badge.warn{background:rgba(251,191,36,0.12);border-color:rgba(251,191,36,0.3);color:var(--warn)}
.badge.success{background:rgba(52,211,153,0.12);border-color:rgba(52,211,153,0.3);color:var(--success)}
.badge.danger{background:rgba(248,113,113,0.12);border-color:rgba(248,113,113,0.3);color:var(--danger)}
.badge.info{background:rgba(34,211,238,0.12);border-color:rgba(34,211,238,0.3);color:var(--accent-2)}

.btn{
    padding:9px 18px;font-size:14px;font-weight:500;
    border:1px solid var(--border);background:var(--bg-card);
    color:var(--text-0);border-radius:8px;transition:all .15s;
}
.btn:hover{background:var(--bg-card-h);border-color:var(--accent)}
.btn.primary{background:linear-gradient(135deg,var(--accent),#5f3edb);border:none}
.btn.primary:hover{filter:brightness(1.15)}
.btn.success{background:linear-gradient(135deg,var(--success),#10b981);border:none;color:#062}
.btn.danger{background:transparent;border-color:var(--danger);color:var(--danger)}
.btn.small{padding:5px 12px;font-size:12px}
.btn:disabled{opacity:.4;cursor:not-allowed}

.page-header{margin-bottom:24px}
.page-header h1{font-size:28px;font-weight:700;letter-spacing:-0.01em}
.page-header .desc{color:var(--text-2);margin-top:4px;font-size:14px}

/* ========== Grid ========== */
.grid{display:grid;gap:16px}
.grid.cols-2{grid-template-columns:repeat(2,1fr)}
.grid.cols-3{grid-template-columns:repeat(3,1fr)}
.grid.cols-4{grid-template-columns:repeat(4,1fr)}
@media(max-width:900px){.grid.cols-3,.grid.cols-4{grid-template-columns:repeat(2,1fr)}}

.stat{padding:20px}
.stat .num{font-size:32px;font-weight:700;
    background:linear-gradient(135deg,var(--accent),var(--accent-2));
    -webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;line-height:1.1}
.stat .label{color:var(--text-2);font-size:12px;margin-top:4px;letter-spacing:1px}
.stat .delta{font-size:12px;margin-top:6px}
.stat .delta.up{color:var(--success)}
.stat .delta.down{color:var(--danger)}

/* ========== Table ========== */
.tbl{width:100%;border-collapse:collapse;font-size:14px}
.tbl th,.tbl td{padding:9px 12px;text-align:left;border-bottom:1px solid var(--border)}
.tbl th{color:var(--text-2);font-weight:500;font-size:12px;letter-spacing:1px;text-transform:uppercase}
.tbl tr:hover td{background:rgba(255,255,255,0.02)}

/* ========== Question ========== */
.q-stem{font-size:16px;line-height:1.7;padding:20px;
    background:rgba(0,0,0,0.2);border-radius:10px;margin-bottom:16px}
.q-options{display:grid;gap:10px;margin-bottom:16px}
.q-option{
    padding:14px 18px;background:var(--bg-card);border:1px solid var(--border);
    border-radius:10px;cursor:pointer;transition:all .15s;
    display:flex;align-items:center;gap:10px;font-size:14px
}
.q-option:hover{background:var(--bg-card-h);border-color:var(--accent)}
.q-option.selected{border-color:var(--accent);background:rgba(124,92,255,0.1)}
.q-option.correct{border-color:var(--success);background:rgba(52,211,153,0.08)}
.q-option.wrong{border-color:var(--danger);background:rgba(248,113,113,0.08)}
.q-option .letter{width:26px;height:26px;flex-shrink:0;border-radius:50%;
    background:var(--bg-card-h);display:flex;align-items:center;justify-content:center;
    font-size:13px;font-weight:600;color:var(--text-1)}
.q-option.selected .letter{background:var(--accent);color:white}
.q-option.correct .letter{background:var(--success);color:#052}
.q-option.wrong .letter{background:var(--danger);color:white}

.q-meta{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:10px}
.q-solution{padding:14px 18px;background:rgba(52,211,153,0.08);border-left:3px solid var(--success);
    border-radius:8px;color:var(--text-1);font-size:14px;margin-top:12px}
.q-solution.wrong{background:rgba(248,113,113,0.08);border-left-color:var(--danger)}

.error-tag-picker{display:flex;flex-wrap:wrap;gap:8px;margin:12px 0}
.error-tag-picker .tag{
    padding:6px 12px;border-radius:100px;font-size:12px;cursor:pointer;
    background:var(--bg-card);border:1px solid var(--border);color:var(--text-1);transition:all .1s
}
.error-tag-picker .tag:hover{border-color:var(--accent)}
.error-tag-picker .tag.on{background:rgba(124,92,255,0.2);border-color:var(--accent);color:var(--text-0)}

/* ========== Radar Chart placeholder ========== */
.radar-container{position:relative;height:280px}

/* ========== Modal ========== */
.modal-bg{position:fixed;inset:0;background:rgba(0,0,0,0.7);z-index:1000;display:flex;align-items:center;justify-content:center}
.modal{background:var(--bg-1);border:1px solid var(--border);border-radius:var(--radius);
    max-width:600px;width:92%;max-height:85vh;overflow-y:auto;padding:24px}
.modal h2{margin-bottom:14px}
.modal .actions{display:flex;gap:10px;justify-content:flex-end;margin-top:20px}

/* ========== Empty ========== */
.empty{padding:40px;text-align:center;color:var(--text-2)}
.empty .big-icon{font-size:48px;margin-bottom:10px}

/* ========== Mastery Bar ========== */
.mastery-bar{
    width:100%;height:8px;background:rgba(255,255,255,0.06);
    border-radius:100px;overflow:hidden;position:relative;
}
.mastery-bar .fill{height:100%;border-radius:100px;transition:width .3s}
.mastery-bar .fill.low{background:linear-gradient(90deg,var(--danger),#dc2626)}
.mastery-bar .fill.mid{background:linear-gradient(90deg,var(--warn),#f59e0b)}
.mastery-bar .fill.high{background:linear-gradient(90deg,var(--success),#10b981)}

/* ========== Diagnosis Report ========== */
.diag-report{padding:0}
.diag-report h3{color:var(--accent-2);margin:16px 0 8px;font-size:16px}
.diag-chain{padding:14px 18px;background:rgba(124,92,255,0.08);border-left:3px solid var(--accent);
    border-radius:8px;font-family:"JetBrains Mono",Consolas,monospace;font-size:13px;
    white-space:pre-line;line-height:1.9;margin:10px 0}
.diag-report .ai-narrative{padding:16px 20px;background:rgba(34,211,238,0.06);
    border-left:3px solid var(--accent-2);border-radius:8px;margin-top:14px;
    color:var(--text-1);font-size:14px;line-height:1.75;white-space:pre-wrap}

/* ========== Setup Form ========== */
.setup{max-width:640px;margin:60px auto;padding:40px;background:var(--bg-card);
    border:1px solid var(--border);border-radius:var(--radius)}
.setup h1{font-size:26px;margin-bottom:8px}
.setup p.desc{color:var(--text-2);margin-bottom:24px;font-size:14px}
.setup .field{margin-bottom:16px}
.setup .field label{display:block;color:var(--text-1);font-size:13px;margin-bottom:6px}
.setup .field input,.setup .field select{
    width:100%;padding:10px 14px;background:var(--bg-1);border:1px solid var(--border);
    border-radius:8px;color:var(--text-0);font-size:14px;font-family:inherit
}
.setup .field input:focus,.setup .field select:focus{outline:none;border-color:var(--accent)}

/* ========== Path (14-day plan) ========== */
.path-day{padding:14px 18px;background:var(--bg-card);border:1px solid var(--border);
    border-radius:10px;margin-bottom:10px;display:flex;gap:14px;align-items:center}
.path-day .day-num{width:60px;flex-shrink:0;text-align:center}
.path-day .day-num .n{font-size:22px;font-weight:700;color:var(--accent)}
.path-day .day-num .label{font-size:10px;letter-spacing:1px;color:var(--text-2)}
.path-day .task{flex:1}
.path-day .task .title{font-size:14px;font-weight:500;color:var(--text-0)}
.path-day .task .meta{font-size:12px;color:var(--text-2);margin-top:2px}
.path-day.done{opacity:.55}
.path-day.done .title{text-decoration:line-through}
.path-day.today{border-color:var(--accent);background:rgba(124,92,255,0.06)}

/* ========== Habit ========== */
.habit-row{display:flex;align-items:center;padding:12px 16px;background:var(--bg-card);
    border:1px solid var(--border);border-radius:10px;margin-bottom:8px;gap:14px}
.habit-row .icon{font-size:22px}
.habit-row .info{flex:1}
.habit-row .info .name{font-weight:500}
.habit-row .info .streak{font-size:12px;color:var(--text-2);margin-top:2px}
.habit-check{width:36px;height:36px;border-radius:50%;border:2px solid var(--border);
    background:transparent;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all .15s}
.habit-check:hover{border-color:var(--accent)}
.habit-check.done{background:var(--success);border-color:var(--success);color:#062}

/* ========== Toast ========== */
.toast{position:fixed;bottom:30px;right:30px;padding:12px 20px;
    background:var(--bg-1);border:1px solid var(--accent);border-radius:10px;
    color:var(--text-0);box-shadow:var(--shadow);z-index:2000;font-size:14px;
    animation:toastIn .3s}
@keyframes toastIn{from{transform:translateY(20px);opacity:0}to{transform:translateY(0);opacity:1}}

/* ========== Mobile ========== */
@media(max-width:768px){
    :root{--sidebar-w:0}
    .app{flex-direction:column}
    .sidebar{position:relative;width:100%;height:auto;padding:14px}
    .sidebar .nav-item{padding:8px 14px;display:inline-flex;font-size:12px;margin:2px}
    .main{margin-left:0;padding:20px}
}