/* Vào lớp - giao diện chung */
:root {
  --bg: #f3f7fd; --surface: #ffffff; --ink: #14264a; --muted: #667091; --line: #e3e6f2;
  --primary: #2f6bd0; --primary-dk: #2253ad; --primary-soft: #e4eefc; --accent: #ffb547; --accent-soft: #fff3de;
  --ok: #17996a; --ok-soft: #dff5ec; --bad: #d4424e; --bad-soft: #fde8ea; --warn-soft: #fff3de;
  --radius: 16px; --shadow: 0 1px 2px rgba(26, 32, 64, .05), 0 8px 28px rgba(26, 32, 64, .07);
  --font: "Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font-family: var(--font); font-size: 16px; line-height: 1.55; min-height: 100vh; display: flex; flex-direction: column; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; }
h1, h2, h3, h4 { line-height: 1.25; margin: 0 0 .5em; letter-spacing: -.01em; }
h1 { font-size: clamp(1.7rem, 4vw, 2.4rem); } h2 { font-size: 1.4rem; } h3 { font-size: 1.12rem; }
p { margin: 0 0 1em; }
.wrap { width: min(1120px, 100% - 32px); margin-inline: auto; }
main { flex: 1; padding: 28px 0 48px; }
.muted { color: var(--muted); } .small { font-size: .88rem; } .center { text-align: center; }
.row { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; } .row.between { justify-content: space-between; }
.stack > * + * { margin-top: 14px; }
.hidden { display: none !important; }

/* thanh trên */
.top { background: var(--surface); border-bottom: 1px solid var(--line); position: sticky; top: 0; z-index: 20; }
.top .wrap { display: flex; align-items: center; gap: 18px; min-height: 64px; flex-wrap: wrap; padding: 6px 0; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.25rem; color: var(--ink); letter-spacing: -.02em; }
.brand:hover { text-decoration: none; }
.brand img { width: 42px; height: 42px; border-radius: 50%; }
.tabs { display: flex; gap: 4px; margin-left: 8px; }
.tabs a { padding: 9px 16px; border-radius: 999px; color: var(--muted); font-weight: 600; }
.tabs a:hover { background: var(--bg); text-decoration: none; color: var(--ink); }
.tabs a.on { background: var(--primary-soft); color: var(--primary-dk); }
.top .grow { flex: 1; }
.who { display: flex; align-items: center; gap: 10px; }
.role-badge { font-size: .74rem; font-weight: 700; padding: 3px 9px; border-radius: 999px; background: var(--accent-soft); color: #9a5b00; }
.asbar { background: var(--accent-soft); border-bottom: 1px solid #f4dfb8; font-size: .94rem; }
.asbar .wrap { display: flex; gap: 12px; align-items: center; justify-content: center; padding: 8px 0; flex-wrap: wrap; }

/* nút */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 1.5px solid transparent; border-radius: 12px; padding: 10px 18px; font: inherit; font-weight: 600; cursor: pointer; background: var(--primary); color: #fff; transition: background .15s, transform .05s, box-shadow .15s; }
.btn:hover { background: var(--primary-dk); text-decoration: none; }
.btn:active { transform: translateY(1px); }
.btn.ghost { background: transparent; color: var(--primary-dk); border-color: var(--line); }
.btn.ghost:hover { background: var(--primary-soft); }
.btn.soft { background: var(--primary-soft); color: var(--primary-dk); }
.btn.soft:hover { background: #dce1ff; }
.btn.ok { background: var(--ok); } .btn.ok:hover { background: #108059; }
.btn.danger { background: var(--bad-soft); color: var(--bad); } .btn.danger:hover { background: #fbd2d6; }
.btn.sm { padding: 6px 12px; font-size: .9rem; border-radius: 10px; }
.btn:disabled, .btn[aria-disabled="true"] { opacity: .55; cursor: not-allowed; }
:focus-visible { outline: 3px solid rgba(47, 107, 208, .45); outline-offset: 2px; }

/* thẻ */
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow); }
.card.flat { box-shadow: none; }
.grid { display: grid; gap: 18px; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
.pcard { display: flex; flex-direction: column; gap: 10px; padding: 20px; }
.pcard h3 { margin: 0; }
.pcard .sum { color: var(--muted); font-size: .95rem; flex: 1; }
.pcard .foot { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-top: 4px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { font-size: .78rem; font-weight: 600; padding: 3px 10px; border-radius: 999px; background: var(--primary-soft); color: var(--primary-dk); }
.chip.gray { background: #eef0f8; color: var(--muted); } .chip.amber { background: var(--accent-soft); color: #9a5b00; }
.chip.green { background: var(--ok-soft); color: #0b7a53; } .chip.red { background: var(--bad-soft); color: var(--bad); }
.bar { height: 8px; background: #e8ebf7; border-radius: 99px; overflow: hidden; }
.bar > i { display: block; height: 100%; background: linear-gradient(90deg, var(--primary), #6f82ff); border-radius: 99px; transition: width .4s; }
.bar.ok > i { background: var(--ok); }

/* trang chủ */
.hero { display: grid; grid-template-columns: 1.3fr 1fr; gap: 28px; align-items: center; color: var(--ink); border-radius: 26px; padding: 56px 46px; min-height: 340px; margin-bottom: 28px; overflow: hidden; position: relative; background: linear-gradient(90deg, rgba(255,255,255,.96) 0%, rgba(255,255,255,.88) 42%, rgba(255,255,255,.25) 100%), url(/static/img/vaolopbg.png) center 30% / cover no-repeat; box-shadow: var(--shadow); border: 1px solid var(--line); }
.hero h1 { color: var(--ink); } .hero p { color: #35486e; font-size: 1.08rem; max-width: 46ch; }
.hero .art { display: flex; justify-content: center; }
.hero .art img { width: min(240px, 60%); filter: drop-shadow(0 18px 24px rgba(0, 0, 40, .35)); animation: bob 4s ease-in-out infinite; }
.hero .btn.light { background: var(--primary); color: #fff; box-shadow: 0 6px 18px rgba(47,107,208,.35); } .hero .btn.light:hover { background: var(--primary-dk); }
.hero .btn.line { background: rgba(255,255,255,.8); color: var(--primary-dk); border-color: var(--line); } .hero .btn.line:hover { background: #fff; }
@keyframes bob { 50% { transform: translateY(-8px); } }
@media (prefers-reduced-motion: reduce) { .hero .art img { animation: none; } .bar > i { transition: none; } }
.filters { display: flex; gap: 10px; flex-wrap: wrap; margin: 4px 0 22px; }
.filters input, .filters select { flex: 1 1 160px; }
.section-h { display: flex; align-items: baseline; justify-content: space-between; margin: 30px 0 14px; }
.section-h h2 { margin: 0; }
.empty { text-align: center; padding: 38px 18px; color: var(--muted); background: var(--surface); border: 1.5px dashed var(--line); border-radius: var(--radius); }

/* biểu mẫu */
label { display: block; font-weight: 600; margin-bottom: 6px; font-size: .94rem; }
input[type=text], input[type=password], input[type=email], input[type=tel], input[type=number], input[type=search], select, textarea {
  width: 100%; padding: 11px 13px; border: 1.5px solid var(--line); border-radius: 12px; font: inherit; color: var(--ink); background: #fff; }
textarea { min-height: 110px; resize: vertical; line-height: 1.5; }
input:focus, select:focus, textarea:focus { border-color: var(--primary); outline: 0; box-shadow: 0 0 0 3px rgba(47, 107, 208, .15); }
.field { margin-bottom: 16px; } .field .hint { color: var(--muted); font-size: .85rem; margin-top: 4px; }
.cols { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); }
.auth { width: min(460px, 100%); margin: 8px auto; }
.alert { padding: 12px 14px; border-radius: 12px; margin-bottom: 16px; font-size: .95rem; }
.alert.err { background: var(--bad-soft); color: #8e1f2a; } .alert.ok { background: var(--ok-soft); color: #0b6a48; }
.alert.info { background: var(--primary-soft); color: #28359e; } .alert.warn { background: var(--warn-soft); color: #7a4a00; }
.seg { display: inline-flex; background: #eceffa; border-radius: 12px; padding: 4px; gap: 4px; }
.seg label { margin: 0; cursor: pointer; }
.seg input { position: absolute; opacity: 0; pointer-events: none; }
.seg span { display: block; padding: 8px 16px; border-radius: 9px; font-weight: 600; color: var(--muted); }
.seg input:checked + span { background: #fff; color: var(--primary-dk); box-shadow: 0 1px 4px rgba(0, 0, 0, .1); }
.seg input:focus-visible + span { outline: 3px solid rgba(47, 107, 208, .45); }

/* học bài */
.crumbs { margin-bottom: 14px; font-size: .94rem; }
.lessons-list { display: grid; gap: 10px; }
.lrow { display: flex; align-items: center; gap: 14px; padding: 14px 16px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; color: inherit; }
.lrow:hover { border-color: var(--primary); text-decoration: none; box-shadow: var(--shadow); }
.lrow .no { width: 36px; height: 36px; border-radius: 11px; background: var(--primary-soft); color: var(--primary-dk); display: grid; place-items: center; font-weight: 700; flex: none; }
.lrow.done .no { background: var(--ok-soft); color: var(--ok); }
.lrow .t { flex: 1; min-width: 0; } .lrow .t b { display: block; } .lrow .t span { color: var(--muted); font-size: .9rem; }
.lrow .pc { width: 90px; flex: none; text-align: right; font-size: .85rem; color: var(--muted); }
.learn { display: grid; grid-template-columns: minmax(0, 1.7fr) minmax(320px, 1fr); gap: 22px; align-items: start; }
.prose { font-size: 1.05rem; } .prose h3, .prose h4, .prose h5 { margin-top: 1.2em; } .prose ul, .prose ol { padding-left: 1.3em; margin: 0 0 1em; }
.prose li { margin: .25em 0; } .prose code { background: #eef0fb; padding: 1px 6px; border-radius: 6px; font-size: .92em; }
.keys { background: var(--accent-soft); border-radius: 14px; padding: 14px 18px; margin: 18px 0; }
.keys h4 { margin: 0 0 6px; color: #8a5200; } .keys ul { margin: 0; padding-left: 1.2em; }
.ex { border: 1.5px solid var(--line); border-radius: 14px; padding: 16px; margin-bottom: 14px; background: #fff; }
.ex.good { border-color: #9ed9c0; background: #f4fcf8; } .ex.bad { border-color: #f1b5ba; }
.ex .q { font-weight: 600; margin-bottom: 10px; }
.opt { display: flex; gap: 10px; align-items: flex-start; padding: 9px 12px; border: 1.5px solid var(--line); border-radius: 11px; margin-bottom: 8px; cursor: pointer; }
.opt:hover { border-color: var(--primary); } .opt input { margin-top: 5px; accent-color: var(--primary); }
.opt.right { border-color: var(--ok); background: var(--ok-soft); } .opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.fb { margin-top: 10px; padding: 10px 12px; border-radius: 11px; background: #f2f4fc; font-size: .95rem; }
.fb.good { background: var(--ok-soft); color: #0b6a48; } .fb.bad { background: var(--bad-soft); color: #8e1f2a; }
.lessonnav { display: flex; justify-content: space-between; gap: 10px; margin-top: 22px; flex-wrap: wrap; }

/* gia sư AI */
.tutor { position: sticky; top: 84px; display: flex; flex-direction: column; max-height: calc(100vh - 110px); padding: 0; overflow: hidden; }
.tutor header { display: flex; gap: 12px; align-items: center; padding: 14px 16px; border-bottom: 1px solid var(--line); background: linear-gradient(135deg, var(--primary-soft), #f6f2ff); }
.tutor header img { width: 44px; height: 44px; border-radius: 14px; background: #fff; padding: 3px; }
.tutor header b { display: block; } .tutor header span { font-size: .82rem; color: var(--muted); }
.msgs { flex: 1; overflow-y: auto; padding: 16px; display: flex; flex-direction: column; gap: 10px; min-height: 220px; }
.msg { max-width: 88%; padding: 10px 14px; border-radius: 16px; white-space: pre-wrap; word-wrap: break-word; font-size: .97rem; }
.msg.bot { background: #eef0fb; border-bottom-left-radius: 5px; align-self: flex-start; }
.msg.me { background: var(--primary); color: #fff; border-bottom-right-radius: 5px; align-self: flex-end; }
.msg.sys { background: transparent; color: var(--muted); font-size: .85rem; align-self: center; text-align: center; }
.msg.typing { color: var(--muted); }
.suggest { display: flex; flex-wrap: wrap; gap: 6px; padding: 0 16px 10px; }
.suggest button { font: inherit; font-size: .85rem; border: 1px solid var(--line); background: #fff; border-radius: 99px; padding: 5px 11px; cursor: pointer; color: var(--primary-dk); }
.suggest button:hover { background: var(--primary-soft); }
.tutor form { display: flex; gap: 8px; padding: 12px 14px; border-top: 1px solid var(--line); }
.tutor input { flex: 1; }

/* soạn chương trình */
.ed-grid { display: grid; grid-template-columns: 280px minmax(0, 1fr); gap: 20px; align-items: start; }
.ed-side { position: sticky; top: 84px; }
.ed-lessons { list-style: none; margin: 0 0 14px; padding: 0; display: grid; gap: 6px; }
.ed-lessons li { display: flex; gap: 8px; align-items: center; padding: 8px 10px; border-radius: 11px; cursor: pointer; border: 1.5px solid transparent; background: #f6f7fd; }
.ed-lessons li.on { border-color: var(--primary); background: var(--primary-soft); }
.ed-lessons li span { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.ed-ex { border: 1.5px solid var(--line); border-radius: 14px; padding: 14px; margin-bottom: 12px; background: #fafbff; }
.opts-ed { display: grid; gap: 8px; margin-top: 8px; }
.opts-ed div { display: flex; gap: 8px; align-items: center; }
.spinner { width: 22px; height: 22px; border-radius: 50%; border: 3px solid var(--primary-soft); border-top-color: var(--primary); animation: spin 0.9s linear infinite; display: inline-block; vertical-align: middle; }
@keyframes spin { to { transform: rotate(360deg); } }
.savebar { position: sticky; bottom: 0; background: rgba(255, 255, 255, .95); backdrop-filter: blur(6px); border-top: 1px solid var(--line); padding: 12px 0; margin-top: 20px; z-index: 5; }

/* bảng quản trị */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: .94rem; }
th, td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--line); vertical-align: middle; }
th { color: var(--muted); font-size: .82rem; text-transform: uppercase; letter-spacing: .04em; }
.stat { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; margin-bottom: 18px; }
.stat div { background: #fff; border: 1px solid var(--line); border-radius: 14px; padding: 14px 16px; }
.stat b { display: block; font-size: 1.6rem; }

/* chân trang */
.foot { background: var(--surface); border-top: 1px solid var(--line); padding: 22px 0; color: var(--muted); font-size: .88rem; }
.foot .wrap { display: grid; gap: 10px; }
.foot .links { display: flex; gap: 16px; flex-wrap: wrap; }

.toast { position: fixed; left: 50%; bottom: 26px; transform: translateX(-50%); background: #1a2040; color: #fff; padding: 11px 18px; border-radius: 12px; z-index: 99; box-shadow: var(--shadow); max-width: min(92vw, 520px); }

@media (max-width: 860px) {
  .hero { grid-template-columns: 1fr; padding: 26px 22px; } .hero .art { order: -1; } .hero .art img { width: 110px; }
  .learn, .ed-grid { grid-template-columns: 1fr; } .tutor, .ed-side { position: static; max-height: none; }
  .msgs { max-height: 50vh; }
  .tabs { order: 3; width: 100%; margin: 0; overflow-x: auto; } .top .grow { display: none; } .who { margin-left: auto; }
}

/* ---- nền ảnh lớp học cho trang đăng nhập / đăng ký ---- */
body.bg-photo { background: linear-gradient(180deg, rgba(243,247,253,.80), rgba(243,247,253,.94) 70%), url(/static/img/vaolopbg.png) center top / cover fixed no-repeat; }
body.bg-photo .auth { background: rgba(255,255,255,.94); backdrop-filter: blur(6px); box-shadow: 0 20px 50px rgba(20,38,74,.16); }
.auth-logo { display: block; width: 72px; height: 72px; margin: 0 auto 10px; border-radius: 50%; box-shadow: 0 8px 22px rgba(47,107,208,.28); }
.auth h2 { text-align: center; } .auth > p.muted { text-align: center; }
.top { background: rgba(255,255,255,.9); backdrop-filter: blur(10px); }
.hero .art img { width: min(210px, 56%); }
.hero .chips-row { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 16px; }
@media (max-width: 760px) { .hero { padding: 28px 22px; background: linear-gradient(180deg, rgba(255,255,255,.93), rgba(255,255,255,.82)), url(/static/img/vaolopbg.png) center / cover no-repeat; } }

.feat { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.feat li { background: rgba(255,255,255,.86); backdrop-filter: blur(6px); border: 1px solid rgba(255,255,255,.9); border-radius: 16px; padding: 12px 16px; box-shadow: 0 6px 20px rgba(20,38,74,.10); }
.feat b { display: block; color: var(--primary-dk); } .feat span { font-size: .92rem; color: #35486e; }
.hero { background: linear-gradient(90deg, rgba(255,255,255,.97) 0%, rgba(255,255,255,.9) 38%, rgba(255,255,255,.35) 100%), url(/static/img/vaolopbg.png) center 35% / cover no-repeat; }
@media (max-width: 760px) { .feat { display: none; } }

.gbtn { width: 100%; background: #fff; color: #1f2b4d; border-color: var(--line); gap: 10px; margin-bottom: 4px; } .gbtn:hover { background: #f6f8fd; text-decoration: none; }
.or { display: flex; align-items: center; gap: 12px; color: var(--muted); font-size: .85rem; margin: 14px 0; } .or::before, .or::after { content: ""; flex: 1; border-top: 1px solid var(--line); }