:root{
  --paper:#f4f6fb; --card:#fff; --ink:#1a2740; --muted:#64708a; --line:#e2e7f0;
  --accent:#2456a6; --accent2:#1b3f7a; --accent-soft:#eaf1fb;
  --good:#1e7f4f; --good-bg:#e6f4ec; --warn:#b06a12; --warn-bg:#fbf1e2;
  --danger:#b3402c; --danger-bg:#f8e9e6; --gold:#b7823f;
  --radius:12px; --serif:"Georgia",serif;
  --sans:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans","Helvetica Neue",Arial,sans-serif;
  --shadow:0 14px 40px -22px rgba(26,39,64,.4);
}
:root[data-theme="dark"]{
  --paper:#0f1626; --card:#17203300; --card:#172033; --ink:#e8eef9; --muted:#93a1bd; --line:#28344e;
  --accent:#4f86d6; --accent2:#9bc0ee; --accent-soft:#1a2740; --good-bg:rgba(30,127,79,.16);
  --warn-bg:rgba(176,106,18,.16); --danger-bg:rgba(179,64,44,.18);
}
*{box-sizing:border-box}
body{margin:0;background:var(--paper);color:var(--ink);font:15px/1.55 var(--sans);}
a{color:var(--accent);}
h1,h2,h3{font-family:var(--serif);}
button,input,select,textarea{font:inherit;color:inherit;}
button{cursor:pointer;}
.btn{border:1px solid var(--accent);background:var(--accent);color:#fff;border-radius:10px;padding:.55rem 1rem;font-weight:700;}
.btn:hover{background:var(--accent2);border-color:var(--accent2);}
.btn.ghost{background:transparent;color:var(--accent);}
.btn.ghost:hover{background:var(--accent-soft);}
.btn.danger{background:var(--danger);border-color:var(--danger);}
.btn:disabled{opacity:.5;cursor:not-allowed;}
.field{display:flex;flex-direction:column;gap:.25rem;margin-bottom:.7rem;}
.field label{font-size:.82rem;font-weight:600;color:var(--muted);}
input,select,textarea{background:var(--card);border:1px solid var(--line);border-radius:9px;padding:.55rem .7rem;width:100%;}
input:focus,select:focus,textarea:focus{outline:2px solid var(--accent-soft);border-color:var(--accent);}
.muted{color:var(--muted);}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);}

/* ---- shell ---- */
.sm-app{display:grid;grid-template-columns:248px 1fr;min-height:100vh;}
.sm-side{background:#12233f;color:#dfe8f6;padding:1rem .7rem;position:sticky;top:0;height:100vh;overflow:auto;}
.sm-brand{display:flex;align-items:center;gap:.55rem;font-family:var(--serif);font-weight:700;font-size:1.1rem;padding:.3rem .5rem 1rem;}
.sm-brand .logo{width:34px;height:34px;border-radius:9px;background:linear-gradient(135deg,#2f6fd0,#1b3f7a);display:grid;place-items:center;font-size:1.1rem;}
.sm-nav a{display:flex;align-items:center;gap:.6rem;color:#c7d4ea;text-decoration:none;padding:.6rem .7rem;border-radius:9px;font-weight:600;font-size:.94rem;margin-bottom:2px;}
.sm-nav a:hover{background:rgba(255,255,255,.08);color:#fff;}
.sm-nav a.on{background:var(--accent);color:#fff;}
.sm-nav .ic{width:20px;text-align:center;}
.sm-nav .grp{font-size:.7rem;letter-spacing:.08em;text-transform:uppercase;color:#7f90b3;margin:.9rem .7rem .3rem;}
.sm-backdrop{display:none;}   /* chỉ hiện trên mobile khi mở menu — nếu không ẩn, div này chiếm cột 2 của grid làm trống toàn bộ nội dung */
.sm-main{min-width:0;display:flex;flex-direction:column;}
.sm-top{position:sticky;top:0;z-index:20;background:color-mix(in srgb,var(--paper) 88%,transparent);backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);display:flex;align-items:center;gap:1rem;padding:.7rem 1.2rem;}
.sm-top .search{flex:1;max-width:440px;}
.sm-top .who{display:flex;align-items:center;gap:.5rem;font-size:.9rem;}
.sm-content{padding:1.2rem;max-width:1200px;width:100%;margin:0 auto;}
.sm-content h1{font-size:1.5rem;margin:.2rem 0 1rem;}
.badge{display:inline-block;padding:.12rem .55rem;border-radius:999px;font-size:.75rem;font-weight:700;}
.badge.ok{background:var(--good-bg);color:var(--good);}
.badge.warn{background:var(--warn-bg);color:var(--warn);}
.badge.bad{background:var(--danger-bg);color:var(--danger);}
.badge.mute{background:var(--accent-soft);color:var(--muted);}

/* stat cards */
.sm-cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(210px,1fr));gap:.9rem;}
.stat{padding:1rem 1.1rem;text-decoration:none;color:inherit;display:block;transition:transform .15s,box-shadow .15s;}
.stat:hover{transform:translateY(-2px);box-shadow:0 18px 40px -20px rgba(36,86,166,.45);}
.stat .k{font-size:.78rem;text-transform:uppercase;letter-spacing:.05em;color:var(--muted);font-weight:700;}
.stat .v{font-size:1.7rem;font-weight:800;font-family:var(--serif);margin-top:.2rem;}
.stat .sub{font-size:.8rem;color:var(--muted);margin-top:.15rem;}

/* placeholder / states */
.placeholder{padding:2.5rem 1rem;text-align:center;color:var(--muted);}
.placeholder .big{font-size:2.4rem;}
.spinner{display:inline-block;width:22px;height:22px;border:3px solid var(--line);border-top-color:var(--accent);border-radius:50%;animation:spin .7s linear infinite;}
@keyframes spin{to{transform:rotate(360deg)}}

/* toasts + dialog */
#sm-toasts{position:fixed;right:1rem;bottom:1rem;z-index:100;display:flex;flex-direction:column;gap:.5rem;}
.sm-toast{background:var(--ink);color:#fff;padding:.6rem .9rem;border-radius:10px;box-shadow:var(--shadow);transition:opacity .3s;max-width:340px;}
.sm-toast.err{background:var(--danger);} .sm-toast.ok{background:var(--good);}
.sm-ov{position:fixed;inset:0;background:rgba(15,22,38,.55);display:flex;align-items:center;justify-content:center;z-index:120;padding:1rem;}
.sm-dialog{background:var(--card);border-radius:16px;padding:1.4rem;max-width:440px;width:100%;box-shadow:var(--shadow);}
.sm-dialog h3{margin:0 0 .5rem;} .sm-dialog p{color:var(--muted);margin:0 0 1rem;}
.sm-dialog-actions{display:flex;justify-content:flex-end;gap:.5rem;}

/* mobile */
.sm-burger{display:none;background:none;border:1px solid var(--line);border-radius:9px;padding:.35rem .6rem;}
@media(max-width:860px){
  .sm-app{grid-template-columns:1fr;}
  .sm-side{position:fixed;left:-260px;width:248px;z-index:60;transition:left .25s;box-shadow:var(--shadow);}
  .sm-side.open{left:0;}
  .sm-burger{display:inline-block;}
  .sm-backdrop{position:fixed;inset:0;background:rgba(0,0,0,.4);z-index:55;display:none;}
  .sm-backdrop.on{display:block;}
}

/* tables */
.toolbar{display:flex;gap:.6rem;flex-wrap:wrap;align-items:flex-end;margin-bottom:.9rem;}
.toolbar .field{margin:0;}
.sm-table-wrap{overflow-x:auto;}
.sm-table{width:100%;border-collapse:collapse;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;}
.sm-table th{text-align:left;font-size:.76rem;text-transform:uppercase;letter-spacing:.04em;color:var(--muted);padding:.6rem .75rem;border-bottom:2px solid var(--line);white-space:nowrap;cursor:pointer;user-select:none;}
.sm-table th .arw{opacity:.5;font-size:.7rem;}
.sm-table td{padding:.6rem .75rem;border-bottom:1px solid var(--line);vertical-align:middle;}
.sm-table tbody tr:last-child td{border-bottom:0;}
.sm-table tbody tr:hover td{background:var(--accent-soft);}
.avatar{width:38px;height:38px;border-radius:50%;object-fit:cover;background:var(--accent-soft);display:inline-grid;place-items:center;color:var(--accent);font-weight:800;font-size:.9rem;flex:none;}
.row-actions{display:flex;gap:.35rem;flex-wrap:wrap;}
.row-actions .btn{padding:.32rem .6rem;font-size:.82rem;}
.pager{display:flex;gap:.6rem;align-items:center;justify-content:space-between;flex-wrap:wrap;margin-top:.9rem;color:var(--muted);font-size:.88rem;}
.pager .pages{display:flex;gap:.3rem;align-items:center;}
.pager button{padding:.3rem .6rem;border:1px solid var(--line);background:var(--card);border-radius:8px;color:var(--ink);}
.pager button:disabled{opacity:.4;}
.pager select{width:auto;padding:.3rem .5rem;}
@media(max-width:760px){
  .sm-table{border:0;background:transparent;}
  .sm-table thead{display:none;}
  .sm-table,.sm-table tbody{display:block;}
  .sm-table tr{display:block;border:1px solid var(--line);border-radius:12px;margin-bottom:.6rem;padding:.3rem .4rem;background:var(--card);}
  .sm-table td{display:flex;justify-content:space-between;gap:1rem;border:0;padding:.3rem .5rem;text-align:right;}
  .sm-table td::before{content:attr(data-th);font-weight:700;color:var(--muted);text-align:left;}
  .sm-table td.cell-actions{justify-content:flex-end;}
  .sm-table td.cell-actions::before{content:"";}
}

/* big modal (forms) */
.sm-modal{background:var(--card);border-radius:16px;max-width:640px;width:100%;box-shadow:var(--shadow);max-height:92vh;overflow:auto;}
.sm-modal .mh{position:sticky;top:0;background:var(--card);display:flex;align-items:center;justify-content:space-between;padding:1rem 1.3rem;border-bottom:1px solid var(--line);z-index:1;}
.sm-modal .mh h3{margin:0;} .sm-modal .mb{padding:1.1rem 1.3rem;}
.sm-modal .mf{position:sticky;bottom:0;background:var(--card);display:flex;justify-content:flex-end;gap:.5rem;padding:.9rem 1.3rem;border-top:1px solid var(--line);}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:0 1rem;}
@media(max-width:560px){.grid2{grid-template-columns:1fr;}}
.photo-drop{display:flex;align-items:center;gap:1rem;border:2px dashed var(--line);border-radius:12px;padding:.7rem .9rem;cursor:pointer;}
.photo-drop img{width:64px;height:64px;border-radius:50%;object-fit:cover;background:var(--accent-soft);}

/* ---- lịch học (GĐ4) ---- */
.cal-head{display:flex;gap:.7rem;align-items:center;flex-wrap:wrap;margin-bottom:.7rem;}
.cal-grid{display:grid;grid-template-columns:repeat(7,1fr);gap:.5rem;}
.cal-col{min-width:0;display:flex;flex-direction:column;gap:.4rem;}
.cal-col .dh{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:.4rem .5rem;text-align:center;font-size:.85rem;}
.cal-col .dh.today{border-color:var(--accent);outline:2px solid var(--accent-soft);}
.cal-col .dh.holiday{background:var(--danger-bg);}
.sess{background:var(--card);border:1px solid var(--line);border-left:4px solid var(--accent);border-radius:10px;
  padding:.45rem .55rem;font-size:.85rem;cursor:pointer;line-height:1.35;}
.sess:hover{box-shadow:var(--shadow);}
.sess .sname{display:block;font-weight:700;}
.sess.held{border-left-color:var(--good);}
.sess.cancelled{opacity:.55;} .sess.cancelled .sname{text-decoration:line-through;}
.sess.conf{border-color:var(--danger);border-left-color:var(--danger);}
.cal-month{display:grid;grid-template-columns:repeat(7,1fr);gap:.35rem;}
.cal-mhead{text-align:center;font-size:.78rem;font-weight:700;color:var(--muted);padding:.2rem 0;}
.cal-cell{background:var(--card);border:1px solid var(--line);border-radius:10px;min-height:86px;padding:.3rem .35rem;
  cursor:pointer;overflow:hidden;font-size:.78rem;}
.cal-cell:hover{border-color:var(--accent);}
.cal-cell.out{opacity:.45;}
.cal-cell.today{border-color:var(--accent);outline:2px solid var(--accent-soft);}
.cal-cell.holiday{background:var(--danger-bg);}
.cal-cell .dn{font-weight:800;margin-bottom:.15rem;}
.cal-cell .dn .hn{font-weight:600;color:var(--danger);font-size:.7rem;margin-left:.25rem;}
.cal-cell .mini{white-space:nowrap;overflow:hidden;text-overflow:ellipsis;color:var(--ink);}
.cal-cell .mini.cancelled{opacity:.5;text-decoration:line-through;}
.cal-cell .mini.more{color:var(--muted);}
@media(max-width:760px){
  .cal-grid{grid-template-columns:1fr;}
  .cal-month{gap:.2rem;} .cal-cell{min-height:56px;}
}

/* ---- điểm danh (GĐ5) ---- */
.att-row{display:flex;align-items:center;justify-content:space-between;gap:.8rem 1rem;flex-wrap:wrap;padding:.55rem .1rem;border-bottom:1px solid var(--line);}
.att-row:last-child{border-bottom:0;}
.att-who{display:flex;align-items:center;gap:.6rem;min-width:190px;flex:1;}
.att-who b{line-height:1.2;}
.att-seg{display:inline-flex;flex-wrap:wrap;gap:.3rem;align-items:center;}
.att-seg button{padding:.34rem .6rem;border:1px solid var(--line);background:var(--card);border-radius:8px;font-size:.8rem;color:var(--muted);font-weight:700;}
.att-seg button:hover{border-color:var(--accent);color:var(--accent);}
.att-seg button.on{color:#fff;}
.att-seg button.on.ok{background:var(--good);border-color:var(--good);}
.att-seg button.on.warn{background:var(--warn);border-color:var(--warn);}
.att-seg button.on.bad{background:var(--danger);border-color:var(--danger);}
.att-seg button.on.mute{background:var(--muted);border-color:var(--muted);}
.att-seg .att-note-btn{color:var(--muted);}
.att-savebar{position:sticky;bottom:0;background:color-mix(in srgb,var(--paper) 90%,transparent);backdrop-filter:blur(6px);
  display:flex;align-items:center;justify-content:flex-end;gap:.6rem;padding:.8rem .2rem;margin-top:.6rem;border-top:1px solid var(--line);}
.att-savebar .msg{margin-right:auto;}
@media(max-width:620px){
  .att-row{align-items:flex-start;}
  .att-seg{width:100%;}
}

/* ---- học phí / hóa đơn (GĐ6) ---- */
.inv-lines{width:100%;border-collapse:collapse;margin-top:.3rem;}
.inv-lines td{padding:.4rem .1rem;border-bottom:1px solid var(--line);vertical-align:top;}
.inv-lines td.r{text-align:right;white-space:nowrap;font-variant-numeric:tabular-nums;}
.inv-lines tr.sub td{border-top:2px solid var(--line);border-bottom:0;padding-top:.6rem;color:var(--muted);}
.inv-lines tr.tot td{font-weight:800;font-size:1.05rem;border-bottom:0;padding-top:.2rem;}
.inv-lines tr:last-child td{border-bottom:0;}

/* ---- nhắc nhở dashboard (GĐ9) ---- */
.reminders{display:flex;flex-direction:column;gap:.5rem;}
.rem{display:flex;align-items:center;gap:.7rem;padding:.7rem .9rem;border-radius:10px;border:1px solid var(--line);background:var(--card);text-decoration:none;color:inherit;}
.rem:hover{border-color:var(--accent);background:var(--accent-soft);}
.rem .ic{font-size:1.2rem;flex:none;}
.rem .txt{flex:1;min-width:0;}
.rem .go{color:var(--accent);font-weight:600;font-size:.85rem;white-space:nowrap;}

/* ---- biên nhận (in) — GĐ7 ---- */
.receipt-print{padding:.3rem .2rem;color:#111;}
body.printing *{visibility:hidden !important;}
body.printing .receipt-print, body.printing .receipt-print *{visibility:visible !important;}
body.printing .receipt-print{position:fixed;left:0;top:0;width:100%;padding:2rem;background:#fff;color:#000;}
@media print{
  body.printing .sm-ov{position:static;background:none;padding:0;}
}

/* auth page */
.auth-wrap{min-height:100vh;display:grid;place-items:center;padding:1.2rem;
  background:linear-gradient(135deg,#eaf1fb,#f6f1e8);}
.auth-card{background:var(--card);border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);padding:2rem;max-width:400px;width:100%;}
.auth-card h1{font-size:1.5rem;margin:.2rem 0 .3rem;text-align:center;}
.auth-card p.sub{text-align:center;color:var(--muted);margin:0 0 1.3rem;}
.msg{font-size:.86rem;min-height:1.1em;margin:.4rem 0 0;}
.msg.err{color:var(--danger);}