/* ================= Design tokens ================= */
:root {
  --bg: #0b1020;
  --bg-2: #111733;
  --glass: rgba(255, 255, 255, .055);
  --glass-strong: rgba(255, 255, 255, .09);
  --border: rgba(255, 255, 255, .10);
  --border-strong: rgba(255, 255, 255, .20);
  --text: #eef1ff;
  --muted: #9aa3c7;
  --primary: hsl(252, 92%, 68%);
  --primary-2: hsl(196, 95%, 58%);
  --grad: linear-gradient(135deg, hsl(252, 92%, 66%) 0%, hsl(212, 95%, 60%) 55%, hsl(186, 92%, 52%) 100%);
  --correct: hsl(152, 68%, 50%);
  --correct-bg: hsla(152, 68%, 50%, .14);
  --wrong: hsl(352, 90%, 66%);
  --wrong-bg: hsla(352, 90%, 66%, .14);
  --warn: hsl(40, 96%, 62%);
  --radius: 18px;
  --radius-sm: 12px;
  --shadow: 0 10px 40px rgba(0, 0, 0, .35);
  --glow: 0 8px 30px hsla(252, 92%, 66%, .35);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: "Be Vietnam Pro", "Segoe UI", Roboto, Arial, sans-serif;
  background: radial-gradient(1200px 600px at 10% -10%, #1d1f4f 0%, transparent 60%),
              radial-gradient(900px 500px at 110% 10%, #0e3a52 0%, transparent 55%),
              var(--bg);
  background-attachment: fixed;
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-tap-highlight-color: transparent;
  overflow-x: hidden;
}

button, input, textarea { font-family: inherit; }
button { -webkit-appearance: none; appearance: none; }

/* Floating background orbs */
.bg-orbs { position: fixed; inset: 0; pointer-events: none; z-index: 0; overflow: hidden; }
.bg-orbs span {
  position: absolute; border-radius: 50%; filter: blur(80px); opacity: .35;
  animation: float 18s ease-in-out infinite;
}
.bg-orbs span:nth-child(1) { width: 380px; height: 380px; background: hsl(252, 90%, 55%); top: -80px; left: -100px; }
.bg-orbs span:nth-child(2) { width: 320px; height: 320px; background: hsl(190, 90%, 45%); bottom: -60px; right: -80px; animation-delay: -6s; }
.bg-orbs span:nth-child(3) { width: 260px; height: 260px; background: hsl(320, 80%, 50%); top: 45%; left: 55%; opacity: .18; animation-delay: -12s; }
@keyframes float {
  0%, 100% { transform: translate(0, 0) scale(1); }
  50% { transform: translate(40px, -30px) scale(1.08); }
}

.container { position: relative; z-index: 1; max-width: 760px; margin: 0 auto; padding: 28px 18px 64px; }

.view { animation: fadeUp .4s ease; }
.view[hidden] { display: none !important; }
[hidden] { display: none !important; }
@keyframes fadeUp { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: none; } }

.glass {
  background: var(--glass);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

/* ================= Header ================= */
.app-header { text-align: center; margin: 8px 0 26px; }
.logo {
  width: 68px; height: 68px; margin: 0 auto 14px; border-radius: 20px;
  display: grid; place-items: center; font-size: 2rem;
  background: var(--grad); box-shadow: var(--glow);
  animation: bob 4s ease-in-out infinite;
}
@keyframes bob { 50% { transform: translateY(-5px) rotate(-3deg); } }
.app-header h1 {
  font-size: 2rem; font-weight: 800; letter-spacing: -.02em;
  background: linear-gradient(92deg, #fff 10%, #c7c2ff 50%, #8be4ff 90%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.subtitle { color: var(--muted); font-size: .98rem; margin-top: 4px; }

.section-title {
  display: flex; align-items: center; gap: 10px;
  font-size: 1rem; font-weight: 700; margin: 26px 0 12px; color: #dfe3ff;
}
.section-title::before { content: ""; width: 4px; height: 18px; border-radius: 4px; background: var(--grad); }
.section-title.small { font-size: .92rem; margin-top: 24px; }

/* ================= Subject cards ================= */
.subject-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.subject-card {
  position: relative; cursor: pointer; color: var(--text);
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  padding: 22px 12px; font-size: 1rem;
  background: var(--glass); border: 1.5px solid var(--border); border-radius: var(--radius);
  transition: transform .2s, border-color .2s, background .2s, box-shadow .2s;
}
.subject-card:hover { transform: translateY(-3px); border-color: var(--border-strong); background: var(--glass-strong); }
.subject-card.selected {
  border-color: transparent;
  background: linear-gradient(var(--bg-2), var(--bg-2)) padding-box, var(--grad) border-box;
  box-shadow: var(--glow);
}
.subject-icon { font-size: 2.3rem; transition: transform .25s; }
.subject-card:hover .subject-icon, .subject-card.selected .subject-icon { transform: scale(1.1); }
.subject-name { font-weight: 700; font-size: 1.05rem; }
.subject-count { color: var(--muted); font-size: .85rem; }
.subject-card .check {
  position: absolute; top: 10px; right: 10px; width: 24px; height: 24px; border-radius: 50%;
  display: grid; place-items: center; font-size: .75rem; font-weight: 800; color: #fff;
  background: var(--grad); opacity: 0; transform: scale(.5); transition: .2s;
}
.subject-card.selected .check { opacity: 1; transform: scale(1); }

/* ================= Mode cards ================= */
.mode-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.mode-card {
  position: relative; cursor: pointer; text-align: left; color: var(--text);
  display: flex; align-items: center; gap: 12px; padding: 16px;
  background: var(--glass); border: 1.5px solid var(--border); border-radius: var(--radius);
  transition: transform .2s, border-color .2s, background .2s, box-shadow .2s;
}
.mode-card:hover { transform: translateY(-2px); border-color: var(--border-strong); background: var(--glass-strong); }
.mode-card:active { transform: scale(.98); }
.mode-card * { pointer-events: none; }
.mode-icon {
  flex: none; width: 46px; height: 46px; border-radius: 14px; display: grid; place-items: center;
  font-size: 1.4rem; background: rgba(255, 255, 255, .07); transition: background .2s;
}
.mode-body { display: flex; flex-direction: column; flex: 1; min-width: 0; }
.mode-name { font-weight: 700; font-size: 1rem; }
.mode-desc { color: var(--muted); font-size: .8rem; line-height: 1.4; }
.radio-dot {
  flex: none; width: 20px; height: 20px; border-radius: 50%; border: 2px solid var(--border-strong);
  position: relative; transition: .2s;
}
.radio-dot::after {
  content: ""; position: absolute; inset: 3px; border-radius: 50%; background: #fff;
  transform: scale(0); transition: transform .2s;
}
.mode-card.selected {
  border-color: transparent;
  background: linear-gradient(var(--bg-2), var(--bg-2)) padding-box, var(--grad) border-box;
  box-shadow: var(--glow);
}
.mode-card.selected .mode-icon { background: var(--grad); }
.mode-card.selected .radio-dot { border-color: transparent; background: var(--grad); }
.mode-card.selected .radio-dot::after { transform: scale(1); }

/* ================= Options ================= */
.options-card { padding: 4px 18px; }
.opt-row {
  display: flex; flex-direction: column; gap: 10px; padding: 14px 0;
  border-bottom: 1px solid var(--border);
}
.opt-row.inline { flex-direction: row; align-items: center; justify-content: space-between; }
.opt-row:last-child { border-bottom: none; }
.opt-row > label { font-weight: 600; font-size: .93rem; color: #dfe3ff; }

.seg { display: flex; gap: 8px; flex-wrap: wrap; }
.seg.wide { margin-bottom: 14px; }
.seg button {
  cursor: pointer; color: var(--text); font-size: .88rem; font-weight: 500;
  padding: 7px 15px; border-radius: 999px;
  background: rgba(255, 255, 255, .05); border: 1px solid var(--border);
  transition: background .15s, border-color .15s, transform .1s, box-shadow .15s;
}
.seg button:hover { border-color: var(--border-strong); background: rgba(255, 255, 255, .09); }
.seg button:active { transform: scale(.94); }
.seg button.selected { background: var(--grad); border-color: transparent; font-weight: 700; box-shadow: 0 4px 16px hsla(252, 92%, 66%, .35); }

.switch {
  flex: none; width: 52px; height: 30px; border-radius: 999px; border: none; cursor: pointer;
  background: rgba(255, 255, 255, .15); position: relative; transition: background .25s;
}
.switch::after {
  content: ""; position: absolute; top: 3px; left: 3px; width: 24px; height: 24px;
  border-radius: 50%; background: #fff; transition: left .25s cubic-bezier(.4, 1.4, .6, 1);
  box-shadow: 0 2px 6px rgba(0, 0, 0, .35);
}
.switch.on { background: var(--grad); }
.switch.on::after { left: 25px; }

/* ================= Buttons ================= */
.btn {
  cursor: pointer; color: var(--text); font-weight: 600; font-size: .94rem;
  padding: 11px 20px; border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, .06); border: 1px solid var(--border);
  transition: transform .12s, background .2s, border-color .2s, box-shadow .2s, filter .2s;
}
.btn:hover { background: rgba(255, 255, 255, .11); border-color: var(--border-strong); }
.btn:active { transform: scale(.96); }
.btn:disabled { opacity: .35; cursor: not-allowed; transform: none; }
.btn-primary { background: var(--grad); border-color: transparent; box-shadow: var(--glow); color: #fff; }
.btn-primary:hover { background: var(--grad); filter: brightness(1.1); border-color: transparent; }
.btn-ghost { background: transparent; }
.btn-small { padding: 8px 14px; font-size: .84rem; }
.btn-lg { padding: 16px 22px; font-size: 1.05rem; }
.btn-block { display: block; width: 100%; margin-top: 14px; }
.btn-row { display: flex; gap: 10px; margin-top: 16px; flex-wrap: wrap; }
.btn-row.center { justify-content: center; }
.btn.danger { color: var(--wrong); border-color: hsla(352, 90%, 66%, .35); }
.btn.danger:hover { background: var(--wrong-bg); }

/* ================= Quiz ================= */
.quiz-topbar { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-bottom: 14px; }
.topbar-center { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; justify-content: center; }
.mode-badge {
  font-size: .78rem; font-weight: 700; padding: 6px 12px; border-radius: 999px;
  background: rgba(255, 255, 255, .07); border: 1px solid var(--border);
}
.timer {
  font-weight: 700; font-size: .98rem; padding: 6px 14px; border-radius: 999px;
  background: rgba(255, 255, 255, .07); border: 1px solid var(--border); font-variant-numeric: tabular-nums;
}
.timer.low { color: var(--wrong); border-color: var(--wrong); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: .5; } }

.live-stats { display: flex; gap: 8px; justify-content: center; margin-bottom: 12px; flex-wrap: wrap; }
.ls { font-size: .82rem; padding: 4px 12px; border-radius: 999px; background: rgba(255, 255, 255, .05); border: 1px solid var(--border); color: var(--muted); }
.ls b { color: var(--text); }
.ls-correct b { color: var(--correct); }
.ls-wrong b { color: var(--wrong); }

.progress { height: 8px; background: rgba(255, 255, 255, .08); border-radius: 999px; overflow: hidden; margin-bottom: 18px; }
.progress-bar { height: 100%; width: 0; background: var(--grad); border-radius: 999px; transition: width .35s ease; box-shadow: 0 0 12px hsla(196, 95%, 58%, .6); }

.question-card { padding: 24px 22px; animation: fadeUp .3s ease; }
.q-meta { display: flex; justify-content: space-between; align-items: center; color: var(--muted); font-size: .8rem; margin-bottom: 10px; }
.q-index { font-weight: 700; color: #c7c2ff; background: hsla(252, 92%, 66%, .15); padding: 3px 10px; border-radius: 999px; }
.q-text { font-size: 1.08rem; font-weight: 600; margin-bottom: 18px; white-space: pre-wrap; line-height: 1.6; }

.options { display: flex; flex-direction: column; gap: 10px; }
.option {
  width: 100%; text-align: left; color: var(--text); font-size: .96rem; line-height: 1.5;
  display: flex; gap: 12px; align-items: flex-start; padding: 13px 14px; cursor: pointer;
  background: rgba(255, 255, 255, .04); border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  transition: border-color .15s, background .15s, transform .1s;
}
.option:hover { border-color: hsla(252, 92%, 70%, .6); background: hsla(252, 92%, 66%, .08); }
.option:active { transform: scale(.99); }
.option .opt-letter {
  flex: none; width: 28px; height: 28px; border-radius: 9px; display: grid; place-items: center;
  font-weight: 800; font-size: .82rem; background: rgba(255, 255, 255, .08); color: #c7c2ff;
  transition: background .15s, color .15s;
}
.option .opt-text { flex: 1; padding-top: 2px; }
.option .opt-mark { flex: none; font-weight: 800; font-size: 1.15rem; padding-top: 1px; }

.option.selected { border-color: var(--primary); background: hsla(252, 92%, 66%, .15); }
.option.selected .opt-letter { background: var(--grad); color: #fff; }

.option.locked { cursor: default; }
.option.locked:hover { border-color: var(--border); background: rgba(255, 255, 255, .04); }
.option.locked:active { transform: none; }
.option.locked.dim { opacity: .55; }
.option.correct, .option.correct:hover { border-color: var(--correct); background: var(--correct-bg); animation: pop .35s ease; }
.option.correct .opt-letter { background: var(--correct); color: #06281a; }
.option.correct .opt-mark { color: var(--correct); }
.option.wrong, .option.wrong:hover { border-color: var(--wrong); background: var(--wrong-bg); animation: shake .4s ease; }
.option.wrong .opt-letter { background: var(--wrong); color: #fff; }
.option.wrong .opt-mark { color: var(--wrong); }
@keyframes shake { 0%, 100% { transform: translateX(0); } 25% { transform: translateX(-6px); } 50% { transform: translateX(6px); } 75% { transform: translateX(-3px); } }
@keyframes pop { 0% { transform: scale(.98); } 60% { transform: scale(1.015); } 100% { transform: scale(1); } }

.feedback {
  margin-top: 16px; padding: 12px 14px; border-radius: var(--radius-sm); font-weight: 600; font-size: .92rem;
  display: flex; align-items: center; gap: 10px; animation: fadeUp .25s ease;
}
.feedback.ok { background: var(--correct-bg); color: var(--correct); border: 1px solid hsla(152, 68%, 50%, .4); }
.feedback.bad { background: var(--wrong-bg); color: var(--wrong); border: 1px solid hsla(352, 90%, 66%, .4); }
.feedback.info { background: hsla(252, 92%, 66%, .12); color: #c7c2ff; border: 1px solid hsla(252, 92%, 66%, .35); }

.quiz-nav { display: flex; justify-content: space-between; gap: 10px; margin-top: 16px; }
.quiz-nav .btn { flex: 1; }

.nav-legend { display: flex; gap: 14px; flex-wrap: wrap; font-size: .78rem; color: var(--muted); margin-bottom: 10px; }
.nav-legend span { display: inline-flex; align-items: center; gap: 6px; }
.nav-legend i { width: 12px; height: 12px; border-radius: 4px; display: inline-block; border: 1px solid var(--border); }
.nav-legend i.l-ans { background: var(--grad); border: none; }
.nav-legend i.l-ok { background: var(--correct); border: none; }
.nav-legend i.l-bad { background: var(--wrong); border: none; }

.nav-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(42px, 1fr)); gap: 8px; }
.nav-grid button {
  aspect-ratio: 1; border-radius: 10px; cursor: pointer; font-weight: 700; font-size: .85rem;
  color: var(--muted); background: rgba(255, 255, 255, .05); border: 1px solid var(--border);
  transition: transform .12s, background .15s, box-shadow .15s;
}
.nav-grid button:hover { transform: translateY(-2px); border-color: var(--border-strong); }
.nav-grid button.answered { background: var(--grad); color: #fff; border-color: transparent; }
.nav-grid button.correct { background: var(--correct); color: #06281a; border-color: transparent; }
.nav-grid button.wrong { background: var(--wrong); color: #fff; border-color: transparent; }
.nav-grid button.current { box-shadow: 0 0 0 2px var(--bg), 0 0 0 4px #fff; color: var(--text); }
.nav-grid button.answered.current, .nav-grid button.correct.current, .nav-grid button.wrong.current { color: #fff; }

/* ================= Result ================= */
.score-card { padding: 30px 20px; text-align: center; }
.ring {
  --p: 0; --c: var(--primary);
  width: 170px; height: 170px; margin: 0 auto; border-radius: 50%;
  background: conic-gradient(var(--c) calc(var(--p) * 1%), rgba(255, 255, 255, .08) 0);
  display: grid; place-items: center; transition: --p 1s;
  filter: drop-shadow(0 0 18px hsla(252, 92%, 66%, .35));
}
.ring-inner { width: 140px; height: 140px; border-radius: 50%; background: var(--bg-2); display: grid; place-content: center; }
.score-pct { font-size: 2.2rem; font-weight: 800; line-height: 1.1; }
.score-big { font-size: .95rem; color: var(--muted); font-weight: 600; }
.score-msg { margin: 16px 0 18px; font-weight: 600; color: #dfe3ff; }
.score-stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; }
.stat {
  display: flex; flex-direction: column; font-size: 1.35rem; font-weight: 800;
  padding: 10px 4px; border-radius: var(--radius-sm); background: rgba(255, 255, 255, .04); border: 1px solid var(--border);
}
.stat small { font-size: .74rem; font-weight: 500; color: var(--muted); }
.stat.correct { color: var(--correct); }
.stat.wrong { color: var(--wrong); }
.stat.skip { color: var(--warn); }

.review-filter { margin: 22px 0 12px; }
.chk { display: inline-flex; align-items: center; gap: 8px; font-weight: 600; cursor: pointer; }
.chk input { width: 18px; height: 18px; accent-color: hsl(252, 92%, 66%); }
.review-item { padding: 16px; margin-bottom: 12px; border-left: 4px solid var(--correct); }
.review-item.is-wrong { border-left-color: var(--wrong); }
.review-item.is-skip { border-left-color: var(--warn); }
.review-item .q-text { font-size: .98rem; margin-bottom: 10px; }
.rev-opt { border-radius: 10px; padding: 8px 12px; margin-top: 6px; font-size: .9rem; border: 1px solid var(--border); background: rgba(255, 255, 255, .03); }
.rev-opt.user-wrong { background: var(--wrong-bg); border-color: hsla(352, 90%, 66%, .5); }
.rev-opt.correct { background: var(--correct-bg); border-color: hsla(152, 68%, 50%, .5); font-weight: 600; }
.rev-note { font-size: .82rem; color: var(--warn); margin-top: 8px; }

/* ================= Manage ================= */
.manage-toolbar { margin-bottom: 10px; }
.manage-toolbar input, #f-question, .f-opt input[type="text"] {
  width: 100%; padding: 11px 14px; border-radius: var(--radius-sm); font-size: .94rem; color: var(--text);
  background: rgba(255, 255, 255, .05); border: 1px solid var(--border); outline: none; transition: border-color .2s, box-shadow .2s;
}
.manage-toolbar input:focus, #f-question:focus, .f-opt input[type="text"]:focus {
  border-color: var(--primary); box-shadow: 0 0 0 3px hsla(252, 92%, 66%, .25);
}
.manage-count { color: var(--muted); font-size: .86rem; margin: 12px 0; }
.m-item { padding: 14px 16px; margin-bottom: 10px; }
.m-item .m-q { font-weight: 600; font-size: .93rem; margin-bottom: 6px; }
.m-item .m-opts { font-size: .84rem; color: var(--muted); }
.m-item .m-actions { display: flex; gap: 8px; margin-top: 10px; }
.m-badge { display: inline-block; font-size: .7rem; background: hsla(40, 96%, 62%, .15); color: var(--warn); border-radius: 999px; padding: 2px 10px; margin-left: 8px; font-weight: 700; }

/* ================= Modal ================= */
.modal {
  position: fixed; inset: 0; z-index: 50; padding: 16px;
  background: rgba(5, 8, 20, .7); backdrop-filter: blur(6px); -webkit-backdrop-filter: blur(6px);
  display: flex; align-items: center; justify-content: center; animation: fadeIn .2s ease;
}
@keyframes fadeIn { from { opacity: 0; } }
.modal-box {
  width: 100%; max-width: 540px; max-height: 92vh; overflow-y: auto; padding: 24px;
  background: var(--bg-2); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow);
  animation: fadeUp .25s ease;
}
.modal-box.small { max-width: 420px; }
.modal-box h3 { margin-bottom: 12px; font-size: 1.2rem; }
.modal-box p { margin-bottom: 6px; color: var(--muted); }
.fld-label { display: block; font-weight: 600; font-size: .88rem; margin: 14px 0 6px; color: #dfe3ff; }
#f-question { resize: vertical; }
.f-opt { display: flex; gap: 10px; align-items: center; margin-bottom: 8px; }
.f-opt input[type="radio"] { width: 20px; height: 20px; accent-color: var(--correct); flex: none; cursor: pointer; }

.error-msg {
  color: var(--wrong); font-size: .88rem; margin-top: 14px; padding: 10px 14px;
  background: var(--wrong-bg); border: 1px solid hsla(352, 90%, 66%, .35); border-radius: var(--radius-sm);
}

/* ================= Toast ================= */
.toast {
  position: fixed; left: 50%; top: 16px; transform: translateX(-50%); z-index: 60;
  max-width: calc(100% - 32px); text-align: center; pointer-events: none;
  padding: 10px 18px; border-radius: 999px; font-weight: 600; font-size: .9rem;
  background: var(--bg-2); border: 1px solid var(--border-strong); box-shadow: var(--shadow);
  animation: fadeUp .25s ease;
}

/* ================= Responsive ================= */
@media (max-width: 560px) {
  .app-header h1 { font-size: 1.55rem; }
  .mode-grid { grid-template-columns: 1fr; }
  .question-card { padding: 18px 16px; }
  .score-stats { grid-template-columns: repeat(2, 1fr); }
  .mode-badge { display: none; }
}