/* ============================================================
   OnThi — design system
   Dark mac dinh, light qua html[data-theme="light"].
   Accent doi theo mon: body[data-subject="pmg"|"enw"].
   Khong dung font/lib ngoai (app phai chay duoc offline & tu file://).
   ============================================================ */

:root {
  --bg:        #0b1020;
  --bg2:       #111834;
  --card:      #151d3b;
  --card2:     #1c2549;
  --line:      #2a3563;
  --line2:     #3a4784;
  --txt:       #e8ecf8;
  --txt2:      #aab4d8;
  --mut:       #7d88b3;
  --ok:        #34d399;
  --okbg:      #06342a;
  --bad:       #f87171;
  --badbg:     #40151a;
  --warn:      #fbbf24;
  --warnbg:    #3d2c05;
  --info:      #60a5fa;
  --acc:       #38bdf8;
  --acc2:      #0ea5e9;
  --accInk:    #04283a;
  --accSoft:   #0c4a6e;
  --shadow:    0 4px 20px #0006;
  --r:         14px;
  --r2:        10px;
  --side:      232px;
}

html[data-theme="light"] {
  --bg:        #f2f4fb;
  --bg2:       #e8ecf8;
  --card:      #ffffff;
  --card2:     #f4f6fd;
  --line:      #dfe4f3;
  --line2:     #c3cbe6;
  --txt:       #101632;
  --txt2:      #48527a;
  --mut:       #6b769e;
  --ok:        #059669;
  --okbg:      #e7f8f1;
  --bad:       #dc2626;
  --badbg:     #fdecec;
  --warn:      #b45309;
  --warnbg:    #fdf4e3;
  --info:      #2563eb;
  --acc:       #0284c7;
  --acc2:      #0369a1;
  --accInk:    #ffffff;
  --accSoft:   #e0f2fe;
  --shadow:    0 2px 12px #0f172a14;
}

body[data-subject="enw"] {
  --acc:     #a78bfa;
  --acc2:    #8b5cf6;
  --accInk:  #241148;
  --accSoft: #2e1c5c;
}
html[data-theme="light"] body[data-subject="enw"] {
  --acc:     #7c3aed;
  --acc2:    #6d28d9;
  --accInk:  #ffffff;
  --accSoft: #ede9fe;
}

* { box-sizing: border-box; margin: 0; padding: 0 }

html, body { height: 100% }

body {
  background: var(--bg);
  color: var(--txt);
  font: 15px/1.55 "Segoe UI", system-ui, -apple-system, "Helvetica Neue", sans-serif;
  -webkit-font-smoothing: antialiased;
}

::selection { background: var(--acc); color: var(--accInk) }

/* ---------------------------------------------------------- scrollbar -- */
* { scrollbar-width: thin; scrollbar-color: var(--line2) transparent }
*::-webkit-scrollbar { width: 10px; height: 10px }
*::-webkit-scrollbar-thumb { background: var(--line2); border-radius: 6px;
  border: 3px solid transparent; background-clip: content-box }

/* ============================== LAYOUT ============================== */
.app { display: grid; grid-template-columns: var(--side) 1fr; min-height: 100vh }

.side {
  background: var(--bg2); border-right: 1px solid var(--line);
  display: flex; flex-direction: column; gap: 4px; padding: 16px 12px;
  position: sticky; top: 0; height: 100vh; overflow-y: auto;
}
.brand { display: flex; align-items: center; gap: 9px; padding: 4px 8px 14px; }
.brand .logo {
  width: 32px; height: 32px; border-radius: 9px; flex: none;
  background: linear-gradient(135deg, var(--acc), var(--acc2));
  display: grid; place-items: center; font-size: 17px; color: var(--accInk);
}
.brand b { font-size: 15px; letter-spacing: .2px; display: block; line-height: 1.2 }
.brand span { font-size: 11.5px; color: var(--mut) }

.navitem {
  display: flex; align-items: center; gap: 10px; width: 100%;
  padding: 9px 11px; border: 0; border-radius: var(--r2); cursor: pointer;
  background: transparent; color: var(--txt2); font: 500 14px inherit;
  text-align: left; position: relative;
}
.navitem:hover { background: var(--card); color: var(--txt) }
.navitem[data-active="1"] { background: var(--accSoft); color: var(--acc); font-weight: 650 }
.navitem .ico { font-size: 15px; width: 20px; text-align: center; flex: none }
.navitem .pill { margin-left: auto }
.navsep { font-size: 10.5px; text-transform: uppercase; letter-spacing: .8px;
  color: var(--mut); padding: 14px 11px 5px; font-weight: 700 }
.side .foot { margin-top: auto; padding-top: 12px; font-size: 11.5px; color: var(--mut) }

.main { min-width: 0; display: flex; flex-direction: column }

.top {
  position: sticky; top: 0; z-index: 30; display: flex; align-items: center;
  gap: 12px; padding: 11px 20px; background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--line); flex-wrap: wrap;
}
.top .spacer { flex: 1 }

.seg { display: flex; background: var(--card); border: 1px solid var(--line);
  border-radius: 11px; padding: 3px; gap: 3px }
.seg button {
  border: 0; background: transparent; color: var(--txt2); cursor: pointer;
  padding: 7px 15px; border-radius: 8px; font: 600 13.5px inherit; white-space: nowrap;
}
.seg button:hover { color: var(--txt) }
.seg button[data-active="1"] { background: var(--acc); color: var(--accInk) }

.view { padding: 22px 20px 70px; max-width: 1000px; width: 100%; margin: 0 auto }
.view.wide { max-width: 1180px }

/* ============================== ATOMS ============================== */
h1 { font-size: 22px; letter-spacing: -.2px }
h2 { font-size: 17px }
h3 { font-size: 15.5px }
.sub { color: var(--mut); font-size: 13.5px; margin-top: 3px }
.small { font-size: 12.5px; color: var(--mut) }
.mut { color: var(--mut) }
.mono { font-family: ui-monospace, "Cascadia Mono", Consolas, monospace }
.center { text-align: center }
.nowrap { white-space: nowrap }
.hidden { display: none !important }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0) }

.page-head { display: flex; align-items: flex-end; gap: 14px; flex-wrap: wrap; margin-bottom: 18px }
.page-head .spacer { flex: 1 }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--r);
  padding: 18px; margin-bottom: 15px;
}
.card.tight { padding: 14px }
.card.flat { background: var(--card2) }
.card-head { display: flex; align-items: center; gap: 10px; margin-bottom: 13px; flex-wrap: wrap }
.card-head .spacer { flex: 1 }

.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center }
.row.end { justify-content: flex-end }
.row.between { justify-content: space-between }
.col { display: flex; flex-direction: column; gap: 10px }
.grid { display: grid; gap: 11px; grid-template-columns: repeat(auto-fill, minmax(215px, 1fr)) }
.grid.k2 { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)) }
.grid.k4 { grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)) }

hr { border: 0; border-top: 1px solid var(--line); margin: 15px 0 }

/* ------------------------------- buttons ------------------------------- */
.btn {
  border: 1px solid transparent; border-radius: var(--r2); cursor: pointer;
  background: var(--acc); color: var(--accInk); font: 650 14px inherit;
  padding: 10px 17px; display: inline-flex; align-items: center; gap: 7px;
  transition: filter .12s, background .12s;
}
.btn:hover { filter: brightness(1.08) }
.btn:active { filter: brightness(.95) }
.btn.sec { background: var(--card2); color: var(--txt); border-color: var(--line) }
.btn.sec:hover { border-color: var(--line2); background: var(--card2) }
.btn.ghost { background: transparent; color: var(--acc); border-color: transparent }
.btn.ghost:hover { background: var(--accSoft) }
.btn.warn { background: var(--warn); color: #2a1c00 }
.btn.danger { background: transparent; color: var(--bad); border-color: var(--bad) }
.btn.danger:hover { background: var(--badbg) }
.btn.lg { padding: 13px 22px; font-size: 15px; border-radius: 12px }
.btn.sm { padding: 6px 11px; font-size: 12.5px; border-radius: 8px }
.btn.block { width: 100%; justify-content: center }
.btn:disabled { opacity: .45; cursor: not-allowed; filter: none }
.btn .kbd { opacity: .65; font-size: 11px }

.kbd {
  font: 600 11px ui-monospace, Consolas, monospace; padding: 2px 5px;
  border: 1px solid var(--line2); border-radius: 5px; color: var(--txt2);
  background: var(--card2); white-space: nowrap;
}

/* ------------------------------- inputs ------------------------------- */
label.lbl { display: block; font-size: 12.5px; color: var(--mut); margin-bottom: 5px; font-weight: 600 }
input[type=text], input[type=password], input[type=number], input[type=date], select, textarea {
  width: 100%; background: var(--card2); color: var(--txt);
  border: 1px solid var(--line); border-radius: var(--r2);
  padding: 9px 11px; font: inherit; outline: 0;
}
input:focus, select:focus, textarea:focus { border-color: var(--acc) }
textarea { resize: vertical; min-height: 110px; line-height: 1.6 }
input[type=checkbox], input[type=radio] { accent-color: var(--acc); width: 15px; height: 15px }
.field { min-width: 130px; flex: 1 }
.field.narrow { max-width: 110px; flex: none }

.check {
  display: flex; align-items: center; gap: 8px; background: var(--card2);
  border: 1px solid var(--line); border-radius: var(--r2); padding: 9px 11px;
  cursor: pointer; font-size: 13.5px; user-select: none;
}
.check:hover { border-color: var(--line2) }
.check input:checked ~ .cnt { color: var(--txt) }
.check .cnt { margin-left: auto; font-size: 11.5px; color: var(--mut) }
.check.on { border-color: var(--acc) }

.switch { display: inline-flex; align-items: center; gap: 9px; cursor: pointer; font-size: 13.5px }

/* ------------------------------- badges ------------------------------- */
.tag {
  display: inline-block; background: var(--card2); color: var(--acc);
  font-size: 11.5px; font-weight: 600; padding: 3px 9px; border-radius: 99px;
  border: 1px solid var(--line);
}
.pill { font-size: 11.5px; font-weight: 700; padding: 2px 9px; border-radius: 99px;
  background: var(--card2); color: var(--txt2); border: 1px solid var(--line) }
.pill.ok { background: var(--okbg); color: var(--ok); border-color: transparent }
.pill.bad { background: var(--badbg); color: var(--bad); border-color: transparent }
.pill.warn { background: var(--warnbg); color: var(--warn); border-color: transparent }
.pill.acc { background: var(--accSoft); color: var(--acc); border-color: transparent }

.chip {
  display: inline-flex; align-items: center; gap: 7px; background: var(--card);
  border: 1px solid var(--line); border-radius: 99px; padding: 6px 13px; font-size: 13px;
}
.chip b { color: var(--acc) }

/* ------------------------------ progress ------------------------------ */
.bar { height: 6px; background: var(--card2); border-radius: 99px; overflow: hidden }
.bar > i { display: block; height: 100%; background: var(--acc); border-radius: 99px;
  transition: width .3s ease }
.bar.thin { height: 4px }
.bar > i.ok { background: var(--ok) } .bar > i.bad { background: var(--bad) }
.bar > i.warn { background: var(--warn) }

.timer { font: 800 16px ui-monospace, Consolas, monospace; color: var(--warn) }
.timer.low { color: var(--bad) }
.timer.calm { color: var(--txt2) }

/* ---------------------------- kpi / stats ---------------------------- */
.kpi { background: var(--card2); border: 1px solid var(--line); border-radius: var(--r2);
  padding: 13px 15px }
.kpi .n { font-size: 25px; font-weight: 800; letter-spacing: -.5px; line-height: 1.15 }
.kpi .l { font-size: 12px; color: var(--mut); margin-top: 2px }
.kpi .n.ok { color: var(--ok) } .kpi .n.bad { color: var(--bad) }
.kpi .n.warn { color: var(--warn) } .kpi .n.acc { color: var(--acc) }

.tbar { display: flex; align-items: center; gap: 10px; margin-bottom: 7px; font-size: 13.5px }
.tbar .nm { width: 210px; flex: none; overflow: hidden; text-overflow: ellipsis; white-space: nowrap }
.tbar .track { flex: 1; height: 9px; background: var(--card2); border-radius: 99px; overflow: hidden }
.tbar .track > i { display: block; height: 100% }
.tbar .vl { width: 96px; flex: none; text-align: right; font-size: 12.5px; color: var(--txt2) }

.heat { display: grid; grid-auto-flow: column; grid-template-rows: repeat(7, 12px);
  gap: 3px; overflow-x: auto; padding-bottom: 4px }
.heat i { width: 12px; height: 12px; border-radius: 3px; background: var(--card2) }
.heat i[data-l="1"] { background: color-mix(in srgb, var(--acc) 30%, var(--card2)) }
.heat i[data-l="2"] { background: color-mix(in srgb, var(--acc) 55%, var(--card2)) }
.heat i[data-l="3"] { background: color-mix(in srgb, var(--acc) 78%, var(--card2)) }
.heat i[data-l="4"] { background: var(--acc) }

.table { width: 100%; border-collapse: collapse; font-size: 13.5px }
.table th, .table td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line) }
.table th { color: var(--mut); font-size: 12px; font-weight: 700; text-transform: uppercase;
  letter-spacing: .4px }
.table tr:last-child td { border-bottom: 0 }
.table td.r, .table th.r { text-align: right }

/* ============================== QUIZ ============================== */
.qhead { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; flex-wrap: wrap }
.qtext { font-size: 17px; font-weight: 600; line-height: 1.5; margin: 12px 0 16px;
  white-space: pre-wrap }

.opt {
  display: flex; gap: 11px; width: 100%; text-align: left; align-items: flex-start;
  background: var(--card2); color: var(--txt); border: 1.5px solid var(--line);
  border-radius: var(--r2); padding: 12px 14px; margin-bottom: 9px; cursor: pointer;
  font: inherit; line-height: 1.5; transition: border-color .12s, background .12s;
}
.opt:hover:not(:disabled) { border-color: var(--line2) }
.opt .ltr {
  flex: none; width: 24px; height: 24px; border-radius: 7px; display: grid;
  place-items: center; background: var(--card); border: 1px solid var(--line);
  font: 700 12.5px ui-monospace, Consolas, monospace; color: var(--txt2);
}
.opt.sel { border-color: var(--acc); background: var(--accSoft) }
.opt.sel .ltr { background: var(--acc); color: var(--accInk); border-color: transparent }
.opt.ok { border-color: var(--ok); background: var(--okbg) }
.opt.ok .ltr { background: var(--ok); color: #04241c; border-color: transparent }
.opt.bad { border-color: var(--bad); background: var(--badbg) }
.opt.bad .ltr { background: var(--bad); color: #3a0d10; border-color: transparent }
.opt:disabled { cursor: default }

.why { border-radius: var(--r2); padding: 12px 14px; margin: 12px 0; font-size: 13.8px;
  line-height: 1.6; border: 1px solid var(--line); background: var(--card2) }
.why.ok { border-color: var(--ok); background: var(--okbg) }
.why.bad { border-color: var(--bad); background: var(--badbg) }
.why b { color: var(--acc) }
.why .lead { display: block; font-weight: 700; margin-bottom: 4px }

.navgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(38px, 1fr)); gap: 6px }
.navgrid button {
  aspect-ratio: 1; border-radius: 8px; border: 1.5px solid var(--line);
  background: var(--card2); color: var(--txt2); cursor: pointer;
  font: 600 12.5px ui-monospace, Consolas, monospace; position: relative;
}
.navgrid button:hover { border-color: var(--line2) }
.navgrid button.answered { background: var(--accSoft); color: var(--acc); border-color: transparent }
.navgrid button.flagged::after {
  content: ""; position: absolute; top: 2px; right: 2px; width: 6px; height: 6px;
  border-radius: 99px; background: var(--warn);
}
.navgrid button.current { border-color: var(--acc); box-shadow: 0 0 0 2px var(--accSoft) }
.navgrid button.ok { background: var(--okbg); color: var(--ok); border-color: transparent }
.navgrid button.bad { background: var(--badbg); color: var(--bad); border-color: transparent }

.legend { display: flex; gap: 14px; flex-wrap: wrap; font-size: 12px; color: var(--mut) }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px;
  margin-right: 5px; vertical-align: -1px; border: 1px solid var(--line) }

.result-score { font-size: 46px; font-weight: 850; letter-spacing: -1.5px; line-height: 1 }
.result-score.ok { color: var(--ok) } .result-score.bad { color: var(--bad) }
.result-score.warn { color: var(--warn) }

.wrongItem { border-left: 3px solid var(--bad); padding: 2px 0 2px 13px; margin-bottom: 16px }
.wrongItem.okItem { border-left-color: var(--ok) }

/* ---------------------------- flashcard ---------------------------- */
.flash {
  min-height: 260px; display: grid; place-items: center; text-align: center;
  padding: 28px 22px; cursor: pointer; user-select: none;
  background: var(--card2); border: 1px solid var(--line); border-radius: var(--r);
}
.flash .fq { font-size: 19px; font-weight: 650; line-height: 1.45; max-width: 620px }
.flash .fa { margin-top: 16px; font-size: 15px; color: var(--ok); font-weight: 700 }
.flash .fe { margin-top: 10px; font-size: 13.5px; color: var(--txt2); line-height: 1.6;
  max-width: 620px }
.flash .hint { margin-top: 18px; font-size: 12px; color: var(--mut) }

/* ---------------------------- writing ---------------------------- */
.wcount { font: 700 13.5px inherit }
.wcount.ok { color: var(--ok) } .wcount.warn { color: var(--warn) } .wcount.mut { color: var(--mut) }
.scenario { background: var(--card2); border: 1px solid var(--line); border-radius: var(--r2);
  padding: 14px 16px; font-size: 13.8px; line-height: 1.65; white-space: pre-wrap;
  max-height: 260px; overflow-y: auto }
.req { border-left: 3px solid var(--acc); padding-left: 13px; margin-bottom: 8px }
.req .rq { font-size: 14.2px; line-height: 1.55 }
.phase { display: flex; gap: 6px; font-size: 12px; color: var(--mut); flex-wrap: wrap }
.phase span { padding: 3px 9px; border-radius: 99px; background: var(--card2);
  border: 1px solid var(--line) }
.phase span.on { background: var(--accSoft); color: var(--acc); border-color: transparent;
  font-weight: 700 }
.crit { margin: 12px 0 }
.crit .hd { display: flex; justify-content: space-between; font-size: 13.5px; gap: 10px }
.fix { background: var(--warnbg); border: 1px solid color-mix(in srgb, var(--warn) 35%, transparent);
  border-radius: var(--r2); padding: 10px 13px; margin: 7px 0; font-size: 13.5px; line-height: 1.55 }
.rewrite { background: var(--accSoft); border-radius: var(--r2); padding: 12px 14px;
  font-size: 13.8px; font-style: italic; line-height: 1.6 }
.ck { display: flex; gap: 9px; align-items: flex-start; font-size: 13.5px; padding: 5px 0;
  cursor: pointer; line-height: 1.5 }

/* ---------------------------- browse ---------------------------- */
.qrow { border: 1px solid var(--line); border-radius: var(--r2); padding: 13px 15px;
  margin-bottom: 9px; background: var(--card2) }
.qrow .qq { font-size: 14.3px; font-weight: 600; line-height: 1.5 }
.qrow .ans { color: var(--ok); font-size: 13.5px; margin-top: 7px; line-height: 1.5 }
.qrow .ex { color: var(--txt2); font-size: 13px; margin-top: 5px; line-height: 1.6 }

/* ---------------------------- toast / modal ---------------------------- */
.toast-wrap { position: fixed; right: 16px; bottom: 16px; z-index: 200; display: flex;
  flex-direction: column; gap: 9px; align-items: flex-end }
.toast {
  background: var(--card); border: 1px solid var(--line2); border-left: 3px solid var(--acc);
  border-radius: var(--r2); padding: 11px 15px; font-size: 13.5px; box-shadow: var(--shadow);
  max-width: 330px; animation: tin .18s ease-out;
}
.toast.ok { border-left-color: var(--ok) }
.toast.bad { border-left-color: var(--bad) }
.toast.warn { border-left-color: var(--warn) }
@keyframes tin { from { opacity: 0; transform: translateY(8px) } }

.modal-back {
  position: fixed; inset: 0; z-index: 300; background: #0008; backdrop-filter: blur(3px);
  display: grid; place-items: center; padding: 20px;
}
.modal {
  background: var(--card); border: 1px solid var(--line2); border-radius: var(--r);
  padding: 20px; max-width: 480px; width: 100%; box-shadow: var(--shadow);
  animation: tin .16s ease-out;
}
.modal h3 { margin-bottom: 9px }
.modal p { font-size: 13.8px; color: var(--txt2); line-height: 1.6 }
.modal .row { margin-top: 17px; justify-content: flex-end }

.empty { text-align: center; padding: 34px 18px; color: var(--mut); font-size: 13.5px }
.empty .big { font-size: 30px; display: block; margin-bottom: 9px; opacity: .8 }

/* ---------------------------- selftest ---------------------------- */
.st-pass { color: var(--ok); font-weight: 700 }
.st-fail { color: var(--bad); font-weight: 700 }

/* ============================== RESPONSIVE ============================== */
@media (max-width: 900px) {
  .app { grid-template-columns: 1fr }
  .side {
    position: fixed; bottom: 0; left: 0; right: 0; top: auto; height: auto;
    flex-direction: row; overflow-x: auto; overflow-y: hidden; z-index: 50;
    border-right: 0; border-top: 1px solid var(--line); padding: 7px 9px;
    gap: 3px; padding-bottom: max(7px, env(safe-area-inset-bottom));
  }
  .side .brand, .side .foot, .side .navsep { display: none }
  .navitem { flex-direction: column; gap: 3px; font-size: 10.5px; padding: 6px 9px;
    min-width: 62px; text-align: center; font-weight: 600 }
  .navitem .ico { font-size: 17px; width: auto }
  .navitem .pill { display: none }
  .view { padding: 16px 14px 96px }
  .tbar .nm { width: 118px }
}
@media (max-width: 560px) {
  .top { padding: 9px 14px; gap: 9px }
  .seg button { padding: 7px 11px; font-size: 13px }
  h1 { font-size: 19px }
  .card { padding: 15px; border-radius: 12px }
  .qtext { font-size: 16px }
  .result-score { font-size: 38px }
  .grid { grid-template-columns: 1fr }
  .grid.k4 { grid-template-columns: 1fr 1fr }
  .toast-wrap { left: 12px; right: 12px; bottom: 84px }
  .toast { max-width: none }
}

@media print {
  .side, .top, .toast-wrap { display: none }
  body { background: #fff; color: #000 }
}