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

:root {
  --bg: #060b14;
  --bg2: #0d1526;
  --bg3: #111d35;
  --card: rgba(255, 255, 255, 0.04);
  --card-hover: rgba(255, 255, 255, 0.08);
  --border: rgba(255, 255, 255, 0.08);
  --border2: rgba(255, 255, 255, 0.14);

  --green: #22c55e;
  --red: #ef4444;
  --yellow: #eab308;
  --blue: #3b82f6;

  --accent1: #10b981;
  /* emerald */
  --accent2: #06b6d4;
  /* cyan */
  --accent3: #8b5cf6;
  /* purple */

  --text: #f0f4ff;
  --text2: #94a3b8;
  --text3: #64748b;

  --radius: 14px;
  --radius-lg: 22px;
  --shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 24px 64px rgba(0, 0, 0, 0.6);

  --font: 'Inter', sans-serif;
  --font2: 'Space Grotesk', sans-serif;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
}

/* ========================
   PARTICLES
   ======================== */
.particles {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

.particle {
  position: absolute;
  border-radius: 50%;
  opacity: 0.18;
  animation: float linear infinite;
}

@keyframes float {
  0% {
    transform: translateY(100vh) scale(0);
    opacity: 0;
  }

  10% {
    opacity: 0.18;
  }

  90% {
    opacity: 0.18;
  }

  100% {
    transform: translateY(-10vh) scale(1);
    opacity: 0;
  }
}

/* ========================
   PAGE TRANSITIONS
   ======================== */
.page {
  display: none;
  min-height: 100vh;
  position: relative;
  z-index: 1;
  animation: fadeSlideIn 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.page.active {
  display: flex;
  flex-direction: column;
}

@keyframes fadeSlideIn {
  from {
    opacity: 0;
    transform: translateY(24px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ========================
   LANDING PAGE
   ======================== */
#landing-page {
  align-items: center;
  justify-content: flex-start;
  padding: 48px 20px 80px;
  background:
    radial-gradient(ellipse 80% 60% at 50% -20%, rgba(16, 185, 129, 0.15) 0%, transparent 60%),
    radial-gradient(ellipse 60% 40% at 90% 80%, rgba(6, 182, 212, 0.10) 0%, transparent 50%),
    var(--bg);
}

.landing-container {
  width: 100%;
  max-width: 780px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 32px;
}

.logo-badge {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: var(--card);
  border: 1px solid var(--border2);
  border-radius: 999px;
  padding: 8px 20px;
  font-family: var(--font2);
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--accent1);
  backdrop-filter: blur(12px);
}

.logo-icon {
  font-size: 1.3rem;
}

.landing-title {
  font-family: var(--font2);
  font-size: clamp(2.2rem, 6vw, 3.8rem);
  font-weight: 800;
  line-height: 1.1;
  text-align: center;
  letter-spacing: -0.03em;
}

.gradient-text {
  background: linear-gradient(135deg, var(--accent1) 0%, var(--accent2) 50%, var(--accent3) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.landing-subtitle {
  color: var(--text2);
  font-size: 1.05rem;
  text-align: center;
  line-height: 1.7;
  max-width: 560px;
}

/* Stats row */
.stats-row {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  justify-content: center;
}

.stat-card {
  background: var(--card);
  border: 1px solid var(--border2);
  border-radius: var(--radius);
  padding: 18px 28px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  backdrop-filter: blur(12px);
  transition: transform 0.2s, background 0.2s;
}

.stat-card:hover {
  background: var(--card-hover);
  transform: translateY(-2px);
}

.stat-number {
  font-family: var(--font2);
  font-size: 1.8rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent1), var(--accent2));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text3);
  font-weight: 500;
}

/* Topic selector */
.topic-selector {
  width: 100%;
}

.topic-selector h3,
.mode-selector h3 {
  font-family: var(--font2);
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text3);
  margin-bottom: 14px;
  text-align: center;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 10px;
}

.topic-btn {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 10px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  transition: all 0.2s;
  color: var(--text2);
  font-size: 0.82rem;
  font-weight: 500;
  text-align: center;
  user-select: none;
}

.topic-btn:hover {
  background: var(--card-hover);
  border-color: var(--border2);
  transform: translateY(-2px);
}

.topic-btn.selected {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.18), rgba(6, 182, 212, 0.12));
  border-color: var(--accent1);
  color: var(--text);
  box-shadow: 0 0 0 1px var(--accent1), 0 4px 16px rgba(16, 185, 129, 0.2);
}

.topic-btn .topic-icon {
  font-size: 1.5rem;
}

.topic-all-btn {
  grid-column: 1 / -1;
  flex-direction: row;
  justify-content: center;
  gap: 10px;
  padding: 14px;
}

/* Mode selector */
.mode-selector {
  width: 100%;
}

.mode-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}

.mode-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 12px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  transition: all 0.2s;
  user-select: none;
}

.mode-card:hover {
  background: var(--card-hover);
  border-color: var(--border2);
}

.mode-card.active {
  background: linear-gradient(135deg, rgba(139, 92, 246, 0.2), rgba(6, 182, 212, 0.12));
  border-color: var(--accent3);
  box-shadow: 0 0 0 1px var(--accent3), 0 4px 16px rgba(139, 92, 246, 0.2);
}

.mode-icon {
  font-size: 1.5rem;
}

.mode-name {
  font-weight: 700;
  font-size: 0.88rem;
  color: var(--text);
}

.mode-desc {
  font-size: 0.75rem;
  color: var(--text3);
}

/* Start Button */
.btn-start {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 18px 48px;
  background: linear-gradient(135deg, var(--accent1) 0%, var(--accent2) 100%);
  border: none;
  border-radius: 999px;
  color: #fff;
  font-family: var(--font2);
  font-size: 1.05rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 8px 32px rgba(16, 185, 129, 0.35), 0 2px 8px rgba(16, 185, 129, 0.2);
  transition: all 0.25s;
  letter-spacing: 0.01em;
}

.btn-start:hover {
  transform: translateY(-2px) scale(1.03);
  box-shadow: 0 12px 40px rgba(16, 185, 129, 0.5), 0 2px 8px rgba(16, 185, 129, 0.25);
}

.btn-start:active {
  transform: scale(0.98);
}

/* ========================
   QUIZ PAGE
   ======================== */
#quiz-page {
  min-height: 100vh;
  background:
    radial-gradient(ellipse 70% 50% at 50% 0%, rgba(139, 92, 246, 0.12) 0%, transparent 55%),
    var(--bg);
  padding: 0 0 100px;
}

.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: rgba(6, 11, 20, 0.8);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 14px;
  color: var(--text2);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-back:hover {
  background: var(--card-hover);
  color: var(--text);
}

.quiz-meta {
  display: flex;
  align-items: center;
  gap: 12px;
}

.quiz-topic-badge {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.2), rgba(6, 182, 212, 0.15));
  border: 1px solid rgba(16, 185, 129, 0.3);
  border-radius: 999px;
  padding: 5px 14px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent1);
}

.score-chip {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 5px 14px;
  font-size: 0.85rem;
  color: var(--text2);
  display: flex;
  gap: 6px;
}

.score-chip span:last-child {
  font-weight: 700;
  color: var(--accent1);
}

/* Timer */
.timer-ring {
  position: relative;
  width: 52px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.timer-svg {
  width: 52px;
  height: 52px;
  transform: rotate(-90deg);
}

.timer-bg {
  fill: none;
  stroke: var(--bg3);
  stroke-width: 4;
}

.timer-progress {
  fill: none;
  stroke: var(--accent1);
  stroke-width: 4;
  stroke-linecap: round;
  stroke-dasharray: 150.8;
  stroke-dashoffset: 0;
  transition: stroke-dashoffset 1s linear, stroke 0.5s;
}

.timer-text {
  position: absolute;
  font-family: var(--font2);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text);
}

.timer-ring.hidden {
  opacity: 0;
  pointer-events: none;
}

/* Progress bar */
.progress-bar-wrap {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 12px 24px 0;
}

.progress-bar-track {
  flex: 1;
  height: 6px;
  background: var(--bg3);
  border-radius: 999px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent1), var(--accent2));
  border-radius: 999px;
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.progress-label {
  font-size: 0.78rem;
  color: var(--text3);
  font-weight: 600;
  white-space: nowrap;
}

/* Quiz body */
.quiz-body {
  max-width: 720px;
  margin: 32px auto 0;
  padding: 0 20px;
}

.question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  backdrop-filter: blur(16px);
  box-shadow: var(--shadow);
  animation: fadeSlideIn 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.question-number {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent2);
  margin-bottom: 12px;
}

.question-text {
  font-size: 1.05rem;
  line-height: 1.75;
  color: var(--text);
  margin-bottom: 28px;
  font-weight: 500;
}

/* Options */
.options-grid {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-btn {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  background: rgba(255, 255, 255, 0.03);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  cursor: pointer;
  transition: all 0.2s;
  text-align: left;
  color: var(--text2);
  font-size: 0.93rem;
  line-height: 1.5;
  width: 100%;
  animation: fadeSlideIn 0.3s ease;
}

.option-btn:hover:not(:disabled) {
  background: var(--card-hover);
  border-color: var(--accent2);
  color: var(--text);
  transform: translateX(4px);
}

.option-letter {
  min-width: 28px;
  height: 28px;
  border-radius: 8px;
  background: var(--bg3);
  border: 1px solid var(--border2);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font2);
  font-weight: 700;
  font-size: 0.78rem;
  color: var(--text3);
  transition: all 0.2s;
  flex-shrink: 0;
}

/* States */
.option-btn.correct {
  background: rgba(34, 197, 94, 0.12);
  border-color: var(--green);
  color: #fff;
}

.option-btn.correct .option-letter {
  background: var(--green);
  color: #fff;
  border-color: var(--green);
}

.option-btn.wrong {
  background: rgba(239, 68, 68, 0.12);
  border-color: var(--red);
  color: var(--text2);
}

.option-btn.wrong .option-letter {
  background: var(--red);
  color: #fff;
  border-color: var(--red);
}

.option-btn:disabled {
  cursor: default;
}

/* Footer */
.quiz-footer {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 16px 20px;
  background: rgba(6, 11, 20, 0.9);
  backdrop-filter: blur(16px);
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: center;
  z-index: 10;
}

.btn-next {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 40px;
  background: linear-gradient(135deg, var(--accent3), var(--accent2));
  border: none;
  border-radius: 999px;
  color: #fff;
  font-family: var(--font2);
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.25s;
  box-shadow: 0 6px 24px rgba(139, 92, 246, 0.3);
}

.btn-next:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn-next:not(:disabled):hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 32px rgba(139, 92, 246, 0.4);
}

/* ========================
   EXPLANATION OVERLAY
   ======================== */
.explanation-overlay {
  position: fixed;
  bottom: 80px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 20;
  width: 90%;
  max-width: 680px;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.3s, transform 0.3s;
  transform: translateX(-50%) translateY(16px);
}

.explanation-overlay.show {
  opacity: 1;
  pointer-events: auto;
  transform: translateX(-50%) translateY(0);
}

.explanation-card {
  background: var(--bg2);
  border-radius: var(--radius);
  border: 1px solid var(--border2);
  padding: 16px 20px;
  box-shadow: var(--shadow-lg);
}

.explanation-header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
}

.explanation-icon {
  font-size: 1.2rem;
}

.explanation-title {
  font-weight: 700;
  font-size: 0.95rem;
}

.explanation-text {
  font-size: 0.88rem;
  color: var(--text2);
  line-height: 1.6;
}

/* ========================
   RESULT PAGE
   ======================== */
#result-page {
  align-items: center;
  justify-content: flex-start;
  padding: 48px 20px 80px;
  background:
    radial-gradient(ellipse 70% 50% at 50% 0%, rgba(16, 185, 129, 0.12) 0%, transparent 55%),
    var(--bg);
}

.result-container {
  width: 100%;
  max-width: 640px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
}

.result-trophy {
  font-size: 5rem;
  animation: bounceIn 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
  filter: drop-shadow(0 8px 24px rgba(234, 179, 8, 0.4));
}

@keyframes bounceIn {
  0% {
    transform: scale(0) rotate(-10deg);
    opacity: 0;
  }

  70% {
    transform: scale(1.15) rotate(5deg);
  }

  100% {
    transform: scale(1) rotate(0deg);
    opacity: 1;
  }
}

.result-title {
  font-family: var(--font2);
  font-size: 2.2rem;
  font-weight: 800;
  text-align: center;
}

.result-subtitle {
  color: var(--text2);
  text-align: center;
}

/* Score ring */
.score-ring-wrap {
  position: relative;
  width: 180px;
  height: 180px;
}

.score-ring-svg {
  width: 180px;
  height: 180px;
  transform: rotate(-90deg);
}

.score-ring-bg {
  fill: none;
  stroke: var(--bg3);
  stroke-width: 8;
}

.score-ring-fill {
  fill: none;
  stroke: var(--accent1);
  stroke-width: 8;
  stroke-linecap: round;
  stroke-dasharray: 314.16;
  stroke-dashoffset: 314.16;
  transition: stroke-dashoffset 1.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.score-ring-inner {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
}

.score-percent {
  font-family: var(--font2);
  font-size: 2.4rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent1), var(--accent2));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.score-label-sm {
  font-size: 0.75rem;
  color: var(--text3);
}

/* Result stats */
.result-stats {
  display: flex;
  gap: 20px;
}

.result-stat {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  min-width: 90px;
}

.rs-icon {
  font-size: 1.4rem;
}

.rs-value {
  font-family: var(--font2);
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text);
}

.rs-label {
  font-size: 0.75rem;
  color: var(--text3);
}

/* Grade */
.result-grade {
  font-family: var(--font2);
  font-size: 1.1rem;
  font-weight: 700;
  padding: 10px 28px;
  border-radius: 999px;
  border: 1.5px solid;
}

/* Review */
.result-review {
  width: 100%;
}

.review-title {
  font-family: var(--font2);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text3);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 12px;
  text-align: center;
}

.review-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  margin-bottom: 8px;
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

.review-status {
  font-size: 1rem;
  flex-shrink: 0;
  margin-top: 2px;
}

.review-content {
  flex: 1;
}

.review-q {
  font-size: 0.85rem;
  color: var(--text);
  font-weight: 500;
  margin-bottom: 4px;
}

.review-a {
  font-size: 0.78rem;
  color: var(--text2);
}

.review-a.wrong {
  color: var(--red);
}

.review-a.correct {
  color: var(--green);
}

/* Action buttons */
.result-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
}

.btn-retry,
.btn-home {
  padding: 13px 28px;
  border-radius: 999px;
  font-family: var(--font2);
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.25s;
  border: none;
}

.btn-retry {
  background: linear-gradient(135deg, var(--accent1), var(--accent2));
  color: #fff;
  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.3);
}

.btn-retry:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 28px rgba(16, 185, 129, 0.4);
}

.btn-home {
  background: var(--card);
  border: 1px solid var(--border2);
  color: var(--text);
}

.btn-home:hover {
  background: var(--card-hover);
  transform: translateY(-2px);
}

/* ========================
   RESPONSIVE
   ======================== */
@media (max-width: 600px) {
  .mode-cards {
    grid-template-columns: 1fr;
  }

  .quiz-header {
    padding: 12px 16px;
  }

  .question-card {
    padding: 20px;
  }

  .result-stats {
    gap: 10px;
  }

  .result-stat {
    min-width: 80px;
    padding: 14px 16px;
  }
}

/* ========================
   SHIMMER ANIMATION
   ======================== */
@keyframes shimmer {
  0% {
    background-position: -200% center;
  }

  100% {
    background-position: 200% center;
  }
}

.shimmer {
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.06), transparent);
  background-size: 200%;
  animation: shimmer 2s infinite;
}

/* ========================
   GRADE COLORS
   ======================== */
.grade-s {
  border-color: #f59e0b;
  color: #f59e0b;
}

.grade-a {
  border-color: var(--accent1);
  color: var(--accent1);
}

.grade-b {
  border-color: var(--accent2);
  color: var(--accent2);
}

.grade-c {
  border-color: #f97316;
  color: #f97316;
}

.grade-d {
  border-color: var(--red);
  color: var(--red);
}

/* ========================
   PULSE ANIMATION FOR CORRECT
   ======================== */
@keyframes correctPulse {
  0% {
    box-shadow: 0 0 0 0 rgba(34, 197, 94, 0.6);
  }

  70% {
    box-shadow: 0 0 0 10px rgba(34, 197, 94, 0);
  }

  100% {
    box-shadow: 0 0 0 0 rgba(34, 197, 94, 0);
  }
}

.option-btn.correct {
  animation: correctPulse 0.6s ease-out;
}

/* ========================
   SCROLLBAR
   ======================== */
::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: var(--bg);
}

::-webkit-scrollbar-thumb {
  background: var(--bg3);
  border-radius: 999px;
}