@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:wght@400;600;700&family=DM+Sans:wght@300;400;500;600&family=DM+Mono:wght@400;500&display=swap');

:root {
  --bg: #0f1117;
  --bg2: #161b27;
  --bg3: #1e2535;
  --border: #2a3045;
  --accent: #f5a623;
  --accent2: #e8734a;
  --accent3: #5b8dee;
  --green: #3ecf8e;
  --red: #f87171;
  --text: #e8ecf4;
  --text2: #8b95aa;
  --text3: #5a6478;
  --card: #1a2133;
  --card-hover: #202b3d;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 48px rgba(0,0,0,0.5);
  --transition: all 0.22s cubic-bezier(0.4,0,0.2,1);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'DM Sans', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
  font-size: 15px;
}

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text3); }

/* Typography */
h1, h2, h3, h4 { font-family: 'Playfair Display', serif; line-height: 1.25; }
h1 { font-size: clamp(2rem, 4vw, 3rem); font-weight: 700; }
h2 { font-size: clamp(1.4rem, 3vw, 2rem); font-weight: 600; }
h3 { font-size: clamp(1.1rem, 2vw, 1.4rem); }
p { color: var(--text2); }
code { font-family: 'DM Mono', monospace; font-size: 0.85em; }

/* Layout */
.container { max-width: 900px; margin: 0 auto; padding: 0 24px; }
.page { display: none; min-height: 100vh; padding: 40px 0; animation: fadeIn 0.35s ease; }
.page.active { display: block; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: none; } }
@keyframes slideUp { from { opacity: 0; transform: translateY(20px); } to { opacity: 1; transform: none; } }
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.5; } }
@keyframes spin { to { transform: rotate(360deg); } }
@keyframes popIn { 0% { transform: scale(0.85); opacity: 0; } 70% { transform: scale(1.04); } 100% { transform: scale(1); opacity: 1; } }

/* Header / Nav */
.app-header {
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(8px);
}
.app-header .inner {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  cursor: pointer;
}
.logo-icon {
  width: 34px; height: 34px;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  border-radius: 8px;
  display: grid;
  place-items: center;
  font-size: 17px;
}
.logo-text {
  font-family: 'Playfair Display', serif;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
}
.logo-text span { color: var(--accent); }
.nav-actions { display: flex; gap: 10px; align-items: center; }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 9px 20px;
  border-radius: var(--radius-sm);
  font-family: 'DM Sans', sans-serif;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  border: none;
  transition: var(--transition);
  text-decoration: none;
  white-space: nowrap;
}
.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  box-shadow: 0 2px 12px rgba(245,166,35,0.25);
}
.btn-primary:hover { transform: translateY(-1px); box-shadow: 0 4px 20px rgba(245,166,35,0.35); }
.btn-primary:active { transform: translateY(0); }
.btn-secondary {
  background: var(--bg3);
  color: var(--text);
  border: 1px solid var(--border);
}
.btn-secondary:hover { background: var(--card-hover); border-color: var(--text3); }
.btn-ghost {
  background: transparent;
  color: var(--text2);
  padding: 9px 12px;
}
.btn-ghost:hover { color: var(--text); background: var(--bg3); }
.btn-lg { padding: 13px 28px; font-size: 15px; border-radius: var(--radius); }
.btn-sm { padding: 6px 14px; font-size: 13px; }
.btn-full { width: 100%; justify-content: center; }
.btn:disabled { opacity: 0.45; cursor: not-allowed; transform: none !important; }

/* Cards */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: var(--transition);
}
.card:hover { border-color: var(--text3); }
.card-sm { padding: 16px; }

/* Form Elements */
.form-group { display: flex; flex-direction: column; gap: 8px; }
.form-label {
  font-size: 13px;
  font-weight: 500;
  color: var(--text2);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}
.form-control {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 11px 14px;
  color: var(--text);
  font-family: 'DM Sans', sans-serif;
  font-size: 14px;
  transition: var(--transition);
  outline: none;
  width: 100%;
}
.form-control:focus { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(245,166,35,0.12); }
.form-control::placeholder { color: var(--text3); }
select.form-control { cursor: pointer; appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%238b95aa' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 32px;
}
select.form-control option { background: var(--bg3); }

/* Input with icon */
.input-wrap { position: relative; }
.input-wrap .input-icon { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--text3); font-size: 15px; pointer-events: none; }
.input-wrap .form-control { padding-left: 38px; }
.input-wrap .input-action { position: absolute; right: 10px; top: 50%; transform: translateY(-50%); }

/* Grid */
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; }

/* Tag badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 4px 10px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 500;
}
.badge-easy { background: rgba(62,207,142,0.15); color: var(--green); border: 1px solid rgba(62,207,142,0.25); }
.badge-medium { background: rgba(245,166,35,0.15); color: var(--accent); border: 1px solid rgba(245,166,35,0.25); }
.badge-hard { background: rgba(248,113,113,0.15); color: var(--red); border: 1px solid rgba(248,113,113,0.25); }
.badge-subject { background: rgba(91,141,238,0.15); color: var(--accent3); border: 1px solid rgba(91,141,238,0.25); }

/* Hero section */
.hero {
  text-align: center;
  padding: 60px 24px 40px;
}
.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(245,166,35,0.1);
  border: 1px solid rgba(245,166,35,0.25);
  color: var(--accent);
  padding: 5px 14px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 500;
  margin-bottom: 20px;
}
.hero h1 { margin-bottom: 14px; }
.hero h1 .highlight {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero p { font-size: 1.05rem; max-width: 540px; margin: 0 auto 30px; }

/* Subject selection cards */
.subject-card {
  background: var(--card);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  cursor: pointer;
  transition: var(--transition);
  text-align: center;
  position: relative;
  overflow: hidden;
}
.subject-card::before {
  content: '';
  position: absolute;
  inset: 0;
  opacity: 0;
  transition: opacity 0.22s;
}
.subject-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }
.subject-card.selected { border-color: var(--accent); }
.subject-card.selected::before { opacity: 1; }
.subject-icon { font-size: 2rem; margin-bottom: 10px; display: block; }
.subject-name { font-family: 'Playfair Display', serif; font-size: 1rem; font-weight: 600; color: var(--text); }
.subject-count { font-size: 12px; color: var(--text3); margin-top: 4px; }

/* Math */
.subject-card[data-subject="Math"] { --sc: #5b8dee; }
.subject-card[data-subject="Math"].selected { border-color: var(--sc); background: rgba(91,141,238,0.08); }
/* Physics */
.subject-card[data-subject="Physics"] { --sc: #f5a623; }
.subject-card[data-subject="Physics"].selected { border-color: var(--sc); background: rgba(245,166,35,0.08); }
/* Chemistry */
.subject-card[data-subject="Chemistry"] { --sc: #3ecf8e; }
.subject-card[data-subject="Chemistry"].selected { border-color: var(--sc); background: rgba(62,207,142,0.08); }
/* Biology */
.subject-card[data-subject="Biology"] { --sc: #e8734a; }
.subject-card[data-subject="Biology"].selected { border-color: var(--sc); background: rgba(232,115,74,0.08); }

/* Difficulty selector */
.difficulty-btn {
  background: var(--bg3);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 16px;
  cursor: pointer;
  transition: var(--transition);
  text-align: center;
  font-family: 'DM Sans', sans-serif;
  color: var(--text2);
  font-size: 14px;
  font-weight: 500;
}
.difficulty-btn:hover { border-color: var(--text3); color: var(--text); }
.difficulty-btn.selected-easy { border-color: var(--green); background: rgba(62,207,142,0.1); color: var(--green); }
.difficulty-btn.selected-medium { border-color: var(--accent); background: rgba(245,166,35,0.1); color: var(--accent); }
.difficulty-btn.selected-hard { border-color: var(--red); background: rgba(248,113,113,0.1); color: var(--red); }
.diff-icon { font-size: 1.2rem; display: block; margin-bottom: 4px; }

/* Timer */
.timer-wrap {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 16px;
}
.timer-display {
  font-family: 'DM Mono', monospace;
  font-size: 1.4rem;
  font-weight: 500;
  color: var(--text);
  min-width: 70px;
}
.timer-display.warning { color: var(--accent); animation: pulse 1s infinite; }
.timer-display.danger { color: var(--red); animation: pulse 0.5s infinite; }

/* Quiz Area */
.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
  flex-wrap: wrap;
  gap: 12px;
}
.quiz-meta { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.q-counter {
  font-family: 'DM Mono', monospace;
  font-size: 13px;
  color: var(--text3);
  background: var(--bg3);
  padding: 4px 10px;
  border-radius: 20px;
  border: 1px solid var(--border);
}

/* Progress bar */
.progress-bar-wrap {
  background: var(--bg3);
  height: 6px;
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 28px;
}
.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  border-radius: 3px;
  transition: width 0.4s ease;
}

/* Question card */
.question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 20px;
  animation: slideUp 0.3s ease;
}
.q-number {
  font-size: 12px;
  color: var(--text3);
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 12px;
  font-family: 'DM Mono', monospace;
}
.q-text {
  font-size: 1.05rem;
  color: var(--text);
  line-height: 1.7;
  font-weight: 500;
}

/* Options */
.options-grid { display: flex; flex-direction: column; gap: 10px; margin-top: 20px; }
.option-btn {
  background: var(--bg3);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 18px;
  cursor: pointer;
  transition: var(--transition);
  text-align: left;
  display: flex;
  align-items: flex-start;
  gap: 12px;
  font-family: 'DM Sans', sans-serif;
  font-size: 14px;
  color: var(--text);
  width: 100%;
}
.option-btn:hover:not(:disabled) { border-color: var(--accent); background: rgba(245,166,35,0.06); }
.option-letter {
  width: 26px; height: 26px;
  border-radius: 6px;
  background: var(--border);
  display: grid;
  place-items: center;
  font-size: 12px;
  font-weight: 600;
  font-family: 'DM Mono', monospace;
  flex-shrink: 0;
  color: var(--text2);
  transition: var(--transition);
}
.option-btn:hover:not(:disabled) .option-letter { background: var(--accent); color: #fff; }
.option-btn.selected { border-color: var(--accent3); background: rgba(91,141,238,0.1); }
.option-btn.selected .option-letter { background: var(--accent3); color: #fff; }
.option-btn.correct { border-color: var(--green); background: rgba(62,207,142,0.1); }
.option-btn.correct .option-letter { background: var(--green); color: #fff; }
.option-btn.incorrect { border-color: var(--red); background: rgba(248,113,113,0.1); }
.option-btn.incorrect .option-letter { background: var(--red); color: #fff; }
.option-btn:disabled { cursor: default; }

/* Navigation row */
.quiz-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 16px;
  gap: 10px;
}
.quiz-nav-left { display: flex; gap: 8px; }
.quiz-nav-right { display: flex; gap: 8px; }

/* Flag / bookmark button */
.flag-btn {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 9px 13px;
  cursor: pointer;
  color: var(--text3);
  transition: var(--transition);
  font-size: 16px;
}
.flag-btn:hover { color: var(--accent); border-color: var(--accent); }
.flag-btn.flagged { color: var(--accent); border-color: var(--accent); background: rgba(245,166,35,0.1); }

/* Question mini-map */
.q-map-wrap {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 20px;
}
.q-map-title { font-size: 12px; color: var(--text3); margin-bottom: 10px; text-transform: uppercase; letter-spacing: 0.06em; }
.q-map { display: flex; flex-wrap: wrap; gap: 6px; }
.q-dot {
  width: 28px; height: 28px;
  border-radius: 6px;
  background: var(--bg3);
  border: 1px solid var(--border);
  display: grid;
  place-items: center;
  font-size: 11px;
  font-family: 'DM Mono', monospace;
  cursor: pointer;
  transition: var(--transition);
  color: var(--text3);
}
.q-dot:hover { border-color: var(--accent); color: var(--accent); }
.q-dot.current { border-color: var(--accent3); background: rgba(91,141,238,0.2); color: var(--accent3); font-weight: 600; }
.q-dot.answered { background: rgba(62,207,142,0.15); border-color: var(--green); color: var(--green); }
.q-dot.flagged { background: rgba(245,166,35,0.12); border-color: var(--accent); color: var(--accent); }
.q-dot.skipped { background: rgba(248,113,113,0.1); border-color: var(--red); color: var(--red); }

/* Results page */
.score-ring-wrap { display: flex; justify-content: center; margin: 20px 0 30px; }
.score-ring-svg { transform: rotate(-90deg); }
.score-text { text-anchor: middle; dominant-baseline: middle; }
.score-val { font-family: 'Playfair Display', serif; font-size: 28px; fill: var(--text); font-weight: 700; }
.score-lbl { font-family: 'DM Sans', sans-serif; font-size: 11px; fill: var(--text3); }

.result-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-bottom: 28px; }
.stat-box { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 16px; text-align: center; }
.stat-val { font-family: 'Playfair Display', serif; font-size: 1.8rem; font-weight: 700; }
.stat-lbl { font-size: 12px; color: var(--text3); margin-top: 4px; }
.stat-correct .stat-val { color: var(--green); }
.stat-wrong .stat-val { color: var(--red); }
.stat-skip .stat-val { color: var(--text3); }

/* Review cards */
.review-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 14px;
  transition: var(--transition);
}
.review-card.correct-card { border-left: 3px solid var(--green); }
.review-card.wrong-card { border-left: 3px solid var(--red); }
.review-card.skip-card { border-left: 3px solid var(--text3); }
.review-q { font-size: 0.95rem; color: var(--text); margin-bottom: 12px; line-height: 1.6; }
.review-answer-row { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 10px; }
.answer-chip {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 12px;
  font-weight: 500;
}
.chip-correct { background: rgba(62,207,142,0.15); color: var(--green); }
.chip-wrong { background: rgba(248,113,113,0.15); color: var(--red); }
.chip-skip { background: rgba(255,255,255,0.06); color: var(--text3); }
.explanation-box {
  background: var(--bg3);
  border-radius: var(--radius-sm);
  padding: 12px 14px;
  font-size: 13.5px;
  color: var(--text2);
  line-height: 1.65;
  border-left: 3px solid var(--accent3);
}
.explanation-box .exp-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent3);
  font-weight: 600;
  margin-bottom: 6px;
}
.review-toggle {
  background: none;
  border: none;
  color: var(--text3);
  font-size: 12px;
  cursor: pointer;
  padding: 4px 0;
  font-family: 'DM Sans', sans-serif;
  display: flex;
  align-items: center;
  gap: 4px;
  transition: var(--transition);
}
.review-toggle:hover { color: var(--accent3); }

/* Loading spinner */
.loading-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 60px 20px;
  gap: 16px;
}
.spinner {
  width: 40px; height: 40px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}
.loading-text { color: var(--text2); font-size: 14px; }
.loading-subtext { color: var(--text3); font-size: 12px; }

/* Toast notification */
.toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 18px;
  font-size: 14px;
  color: var(--text);
  box-shadow: var(--shadow);
  z-index: 9999;
  display: flex;
  align-items: center;
  gap: 8px;
  transform: translateY(80px);
  opacity: 0;
  transition: all 0.3s cubic-bezier(0.34,1.56,0.64,1);
  max-width: 320px;
}
.toast.show { transform: none; opacity: 1; }
.toast.success { border-left: 3px solid var(--green); }
.toast.error { border-left: 3px solid var(--red); }
.toast.info { border-left: 3px solid var(--accent3); }

/* Divider */
.divider { height: 1px; background: var(--border); margin: 24px 0; }

/* Section label */
.section-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text3);
  font-weight: 600;
  margin-bottom: 12px;
  font-family: 'DM Mono', monospace;
}

/* API key page */
.apikey-wrap { max-width: 520px; margin: 0 auto; }
.apikey-wrap .card { padding: 32px; }
.api-status {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 20px;
}
.api-status.valid { background: rgba(62,207,142,0.12); color: var(--green); border: 1px solid rgba(62,207,142,0.25); }
.api-status.invalid { background: rgba(248,113,113,0.12); color: var(--red); border: 1px solid rgba(248,113,113,0.25); }
.api-status-dot { width: 7px; height: 7px; border-radius: 50%; background: currentColor; }

/* Setup page */
.setup-section { margin-bottom: 28px; }
.setup-section h3 { margin-bottom: 14px; color: var(--text); font-size: 1.05rem; }

/* Toggle switch */
.toggle-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 16px;
}
.toggle-info { display: flex; flex-direction: column; gap: 2px; }
.toggle-name { font-size: 14px; font-weight: 500; color: var(--text); }
.toggle-desc { font-size: 12px; color: var(--text3); }
.toggle {
  position: relative;
  width: 44px; height: 24px;
  flex-shrink: 0;
}
.toggle input { opacity: 0; width: 0; height: 0; }
.toggle-slider {
  position: absolute; inset: 0;
  background: var(--border);
  border-radius: 12px;
  cursor: pointer;
  transition: var(--transition);
}
.toggle-slider::before {
  content: '';
  position: absolute;
  width: 18px; height: 18px;
  left: 3px; top: 3px;
  background: var(--text3);
  border-radius: 50%;
  transition: var(--transition);
}
.toggle input:checked + .toggle-slider { background: var(--accent); }
.toggle input:checked + .toggle-slider::before { transform: translateX(20px); background: #fff; }

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.7);
  backdrop-filter: blur(4px);
  z-index: 500;
  display: none;
  place-items: center;
  padding: 20px;
}
.modal-overlay.open { display: grid; }
.modal {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  max-width: 480px;
  width: 100%;
  animation: popIn 0.25s ease;
}
.modal h3 { margin-bottom: 10px; }
.modal p { margin-bottom: 20px; font-size: 14px; }
.modal-actions { display: flex; gap: 10px; justify-content: flex-end; }

/* Responsive */
@media (max-width: 640px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr 1fr; }
  .result-stats { grid-template-columns: 1fr 1fr 1fr; }
  .quiz-header { flex-direction: column; align-items: flex-start; }
  .q-map .q-dot { width: 24px; height: 24px; font-size: 10px; }
}
@media (max-width: 420px) {
  .grid-3 { grid-template-columns: 1fr 1fr; }
  .grid-4 { grid-template-columns: 1fr 1fr; }
}