/* ===== Reset & Basis ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:        #0f1117;
  --bg2:       #1a1d27;
  --bg3:       #22273a;
  --border:    #2e3350;
  --text:      #e8eaf6;
  --text2:     #9399b5;
  --accent:    #5b7cfa;
  --accent2:   #7b9cff;
  --green:     #4caf82;
  --red:       #e05c6a;
  --yellow:    #f5a623;
  --premium:   #f0b429;
  --radius:    12px;
  --radius-sm: 8px;
  --shadow:    0 4px 24px rgba(0,0,0,.4);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

html, body {
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 16px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  overscroll-behavior: none;
}

#app {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

/* ===== Auth ===== */
.view {
  min-height: 100dvh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.auth-card {
  width: 100%;
  max-width: 400px;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 24px;
  box-shadow: var(--shadow);
}

.logo {
  font-size: 1.6rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 8px;
  color: var(--accent2);
}

.auth-card h1 {
  font-size: 1.2rem;
  text-align: center;
  color: var(--text2);
  margin-bottom: 24px;
  font-weight: 500;
}

.auth-card form { display: flex; flex-direction: column; gap: 16px; }

.auth-card label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-size: .875rem;
  color: var(--text2);
}

.hint { font-size: .75rem; color: var(--text2); }

.auth-card input {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: 1rem;
  padding: 12px 14px;
  outline: none;
  transition: border-color .2s;
  -webkit-appearance: none;
}
.auth-card input:focus { border-color: var(--accent); }

.auth-links {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  text-align: center;
}
.auth-links a { color: var(--accent2); font-size: .875rem; text-decoration: none; }

.form-error  { margin-top: 12px; color: var(--red);   font-size: .875rem; text-align: center; }
.form-success { margin-top: 12px; color: var(--green); font-size: .875rem; text-align: center; }

/* ===== Main App ===== */
#main-app {
  display: flex;
  flex-direction: column;
  min-height: 100dvh;
}

/* ===== TopBar ===== */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 12px 16px;
  padding-top: max(12px, env(safe-area-inset-top));
  position: sticky;
  top: 0;
  z-index: 100;
}
.topbar-logo { font-weight: 700; font-size: 1.1rem; color: var(--accent2); }
.topbar-right { display: flex; align-items: center; gap: 12px; }

.streak-badge {
  background: rgba(245,166,35,.15);
  color: var(--yellow);
  border-radius: 99px;
  padding: 4px 10px;
  font-size: .85rem;
  font-weight: 600;
}

.btn-icon {
  background: none;
  border: none;
  color: var(--text2);
  font-size: 1.2rem;
  cursor: pointer;
  padding: 4px;
  border-radius: var(--radius-sm);
  transition: color .2s;
}
.btn-icon:hover { color: var(--text); }

/* ===== Ad Banner ===== */
.ad-banner {
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 4px 0;
  min-height: 60px;
  overflow: hidden;
}

/* ===== Content ===== */
#content {
  flex: 1;
  overflow-y: auto;
  padding-bottom: calc(64px + var(--safe-bottom));
}

.view-main { padding: 16px; }

/* ===== Dashboard ===== */
.welcome-banner {
  background: linear-gradient(135deg, var(--bg3), #1e2540);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 20px;
  font-size: .95rem;
  color: var(--text2);
}
.welcome-banner strong { color: var(--text); }

.dashboard-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 20px;
}

.dash-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 16px;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 6px;
  cursor: pointer;
  transition: border-color .2s, transform .1s;
  text-align: left;
  position: relative;
  overflow: hidden;
}
.dash-card:active { transform: scale(.97); }
.dash-card:hover  { border-color: var(--accent); }

.dash-icon  { font-size: 1.8rem; }
.dash-label { font-weight: 600; font-size: .95rem; color: var(--text); }
.dash-sub   { font-size: .8rem; color: var(--text2); }

.premium-tag {
  position: absolute;
  top: 8px; right: 8px;
  background: var(--premium);
  color: #000;
  font-size: .65rem;
  font-weight: 700;
  padding: 2px 7px;
  border-radius: 99px;
}

/* ===== Badges Strip (Dashboard) ===== */
.badges-strip {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding-bottom: 4px;
  scrollbar-width: none;
}
.badges-strip::-webkit-scrollbar { display: none; }
.badge-chip {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: 99px;
  padding: 6px 12px;
  font-size: .8rem;
  white-space: nowrap;
  flex-shrink: 0;
}

/* ===== View Header ===== */
.view-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}
.view-header h2 { flex: 1; font-size: 1.1rem; font-weight: 600; }
.progress-text  { font-size: .85rem; color: var(--text2); white-space: nowrap; }

.btn-back {
  background: none;
  border: none;
  color: var(--accent2);
  font-size: .9rem;
  cursor: pointer;
  padding: 4px 0;
  white-space: nowrap;
}

/* ===== Progress Bar ===== */
.progress-bar-wrap {
  background: var(--bg3);
  border-radius: 99px;
  height: 4px;
  margin-bottom: 20px;
  overflow: hidden;
}
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  border-radius: 99px;
  width: 0%;
  transition: width .4s ease;
}

/* ===== Flashcard ===== */
#fc-container { display: flex; flex-direction: column; gap: 14px; }

.flashcard {
  perspective: 1000px;
  height: 280px;
  cursor: pointer;
}
.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform .5s ease;
}
.card-inner.flipped { transform: rotateY(180deg); }

.card-front, .card-back {
  position: absolute;
  inset: 0;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 12px;
  overflow-y: auto;
}
.card-back { transform: rotateY(180deg); background: var(--bg3); }

.card-category {
  font-size: .75rem;
  text-transform: uppercase;
  letter-spacing: .05em;
  color: var(--accent);
  font-weight: 600;
}
.card-front p { font-size: 1rem; font-weight: 600; line-height: 1.5; }
.card-back p   { font-size: .95rem; line-height: 1.5; }
.card-explanation { color: var(--text2); font-size: .875rem !important; }
.card-ref { font-size: .75rem !important; color: var(--accent); }

/* ===== Rating Buttons ===== */
.rating-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr 1fr;
  gap: 8px;
}
.btn-rate {
  border: none;
  border-radius: var(--radius-sm);
  padding: 12px 4px;
  font-size: .8rem;
  font-weight: 600;
  cursor: pointer;
  transition: opacity .2s, transform .1s;
}
.btn-rate:active { transform: scale(.95); }
.btn-rate-wrong { background: rgba(224,92,106,.2); color: var(--red); }
.btn-rate-hard  { background: rgba(245,166,35,.15); color: var(--yellow); }
.btn-rate-ok    { background: rgba(76,175,130,.2);  color: var(--green); }
.btn-rate-easy  { background: rgba(91,124,250,.2);  color: var(--accent2); }

/* ===== Quiz / Exam ===== */
.question-category {
  font-size: .75rem;
  text-transform: uppercase;
  letter-spacing: .05em;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 8px;
}
.question-text {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.5;
  margin-bottom: 16px;
}

.choices-list { display: flex; flex-direction: column; gap: 10px; }

.choice-btn {
  background: var(--bg2);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: .95rem;
  line-height: 1.4;
  padding: 14px 16px;
  text-align: left;
  cursor: pointer;
  transition: border-color .2s, background .2s;
  width: 100%;
}
.choice-btn:active { transform: scale(.99); }
.choice-btn:hover  { border-color: var(--accent); }
.choice-btn.selected { border-color: var(--accent); background: rgba(91,124,250,.1); }
.choice-btn.correct  { border-color: var(--green); background: rgba(76,175,130,.15); color: var(--green); }
.choice-btn.wrong    { border-color: var(--red);   background: rgba(224,92,106,.1);  color: var(--red);   }
.choice-btn:disabled { cursor: default; }

.explanation-box {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px;
  font-size: .875rem;
  color: var(--text2);
  margin-top: 4px;
  line-height: 1.5;
}

/* ===== Exam Timer ===== */
.exam-timer {
  font-size: 1rem;
  font-weight: 700;
  color: var(--accent2);
  font-variant-numeric: tabular-nums;
}
.exam-timer.warning { color: var(--red); }

/* ===== Done / Result Screens ===== */
.done-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 32px 16px;
  text-align: center;
}
.done-icon { font-size: 3rem; }
.done-screen h3 { font-size: 1.2rem; }
.done-screen p  { color: var(--text2); }

.result-circle {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  background: conic-gradient(var(--green) var(--pct, 0%), var(--bg3) 0%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 700;
  position: relative;
}
.result-circle::before {
  content: '';
  position: absolute;
  inset: 10px;
  background: var(--bg);
  border-radius: 50%;
}
.result-circle span { position: relative; z-index: 1; }

/* ===== Stats / Progress ===== */
.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 24px;
}
.stat-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}
.stat-value { font-size: 2rem; font-weight: 700; color: var(--accent2); }
.stat-label { font-size: .8rem; color: var(--text2); text-align: center; }

.section-title { font-size: 1rem; font-weight: 600; margin-bottom: 12px; color: var(--text2); }

.badges-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}
.badge-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  text-align: center;
}
.badge-card .badge-icon { font-size: 1.8rem; }
.badge-card .badge-name { font-size: .85rem; font-weight: 600; }
.badge-card .badge-desc { font-size: .75rem; color: var(--text2); }

/* ===== Premium Wall ===== */
.premium-wall {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 40px 24px;
  text-align: center;
}
.premium-wall-icon { font-size: 3rem; }
.premium-wall h3   { font-size: 1.2rem; }
.premium-wall p    { color: var(--text2); font-size: .95rem; }

/* ===== Buttons ===== */
.btn {
  border: none;
  border-radius: var(--radius);
  font-size: .95rem;
  font-weight: 600;
  padding: 14px 24px;
  cursor: pointer;
  transition: opacity .2s, transform .1s;
  text-align: center;
  display: inline-block;
}
.btn:active   { transform: scale(.97); }
.btn-primary  { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent2); }
.btn-outline  { background: transparent; border: 1.5px solid var(--border); color: var(--text); }
.btn-outline:hover { border-color: var(--accent); }
.btn-premium  { background: var(--premium); color: #000; }
.btn-full     { width: 100%; }

/* ===== Bottom Nav ===== */
.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0; right: 0;
  background: var(--bg2);
  border-top: 1px solid var(--border);
  display: flex;
  padding-bottom: var(--safe-bottom);
  z-index: 100;
}
.nav-btn {
  flex: 1;
  background: none;
  border: none;
  color: var(--text2);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  padding: 10px 4px;
  cursor: pointer;
  transition: color .2s;
  font-size: .65rem;
}
.nav-btn.active { color: var(--accent2); }
.nav-icon { font-size: 1.3rem; line-height: 1; }
.nav-label { font-size: .6rem; }

/* ===== Toast ===== */
.toast {
  position: fixed;
  bottom: calc(72px + var(--safe-bottom));
  left: 50%;
  transform: translateX(-50%);
  background: var(--bg3);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 20px;
  border-radius: 99px;
  font-size: .875rem;
  z-index: 999;
  white-space: nowrap;
  box-shadow: var(--shadow);
  animation: fadeInOut 3s ease forwards;
}
@keyframes fadeInOut {
  0%   { opacity: 0; transform: translateX(-50%) translateY(8px); }
  15%  { opacity: 1; transform: translateX(-50%) translateY(0); }
  80%  { opacity: 1; }
  100% { opacity: 0; }
}

/* ===== Utilities ===== */
[hidden] { display: none !important; }
.text-center { text-align: center; }