@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;600;700&display=swap');

:root{
  --bg-1: #021233;
  --bg-2: #052a5f;
  --card-bg: rgba(255,255,255,0.94);
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-2: #06b6d4;
  --success: #10b981;
  --danger: #ef4444;
  --glass-blur: 8px;
  --radius-lg: 16px;
  --radius-sm: 10px;
  --shadow-1: 0 8px 30px rgba(3,7,18,0.55);
  --shadow-2: 0 6px 18px rgba(2,6,23,0.12);
}


* { box-sizing: border-box; margin: 0; padding: 0; }
html,body { height: 100%; }
body{
  font-family: 'Poppins', system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  background: linear-gradient(135deg, var(--bg-1) 0%, var(--bg-2) 100%);
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  color: #0b1220;
}


.app{
  width: 100%;
  max-width: 760px;
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow-1);
  backdrop-filter: blur(var(--glass-blur));
  border: 1px solid rgba(255,255,255,0.35);
  transform-origin: center;
  transition: transform 300ms ease, box-shadow 300ms ease;
}
.app:hover{ transform: translateY(-4px); box-shadow: 0 18px 45px rgba(2,6,23,0.5); }


.app h1{
  font-size: 20px;
  font-weight: 700;
  color: #071034;
  letter-spacing: -0.2px;
  margin-bottom: 14px;
  display: inline-block;
}
.app h1::after{
  content: "";
  display: block;
  height: 4px;
  width: 60px;
  border-radius: 4px;
  margin-top: 12px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
}


.quiz{
  padding-top: 18px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}


.quiz h2{
  font-size: 18px;
  color: #071034;
  font-weight: 600;
  line-height: 1.35;
  margin-bottom: 4px;
}


#answer-buttons{
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin-top: 6px;
}


.btn{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  background: linear-gradient(180deg, #ffffff 0%, #fbfdff 100%);
  color: #0b1220;
  font-weight: 600;
  width: 100%;
  border: 1px solid rgba(7,16,36,0.06);
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  text-align: left;
  box-shadow: var(--shadow-2);
  transition: transform 180ms cubic-bezier(.2,.9,.3,1), box-shadow 180ms, background 180ms, color 180ms;
  position: relative;
  overflow: hidden;
  min-height: 54px;
}


.btn span.option-text{
  display: inline-block;
  flex: 1 1 auto;
}


.btn:hover:not([disabled]){
  transform: translateY(-6px);
  box-shadow: 0 14px 34px rgba(3,7,18,0.12);
}
.btn:focus{
  outline: none;
  box-shadow: 0 0 0 4px rgba(37,99,235,0.14);
}


.btn:disabled{
  cursor: not-allowed;
  opacity: 0.6;
  transform: none;
  box-shadow: none;
}


.btn.correct{
  background: linear-gradient(90deg, rgba(16,185,129,0.12), rgba(16,185,129,0.06));
  border-color: rgba(16,185,129,0.25);
  color: #064e3b;
}
.btn.correct::after{
  content: "✓";
  font-weight: 700;
  color: var(--success);
  background: rgba(16,185,129,0.12);
  height: 34px;
  width: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  font-size: 14px;
  margin-left: 12px;
}


.btn.incorrect{
  background: linear-gradient(90deg, rgba(239,68,68,0.08), rgba(239,68,68,0.04));
  border-color: rgba(239,68,68,0.18);
  color: #7f1d1d;
}
.btn.incorrect::after{
  content: "✕";
  font-weight: 700;
  color: var(--danger);
  background: rgba(239,68,68,0.06);
  height: 34px;
  width: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  font-size: 14px;
  margin-left: 12px;
}


#next-btn{
  appearance: none;
  border: 0;
  display: inline-block;
  padding: 12px 20px;
  border-radius: 12px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: white;
  font-weight: 700;
  cursor: pointer;
  width: auto;
  align-self: center;
  box-shadow: 0 10px 30px rgba(37,99,235,0.18);
  transition: transform 160ms, box-shadow 160ms, opacity 160ms;
}
#next-btn:hover{ transform: translateY(-4px); box-shadow: 0 18px 40px rgba(37,99,235,0.2); }
#next-btn:active{ transform: translateY(-1px); }


.app .meta{
  color: var(--muted);
  font-size: 13px;
}


@keyframes fadeUp {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}
#answer-buttons .btn{
  animation: fadeUp 360ms ease forwards;
}
#answer-buttons .btn:nth-child(1){ animation-delay: 40ms; }
#answer-buttons .btn:nth-child(2){ animation-delay: 90ms; }
#answer-buttons .btn:nth-child(3){ animation-delay: 140ms; }
#answer-buttons .btn:nth-child(4){ animation-delay: 190ms; }


@media (max-width: 520px){
  .app{
    padding: 20px;
    border-radius: 12px;
  }
  .app h1{ font-size: 18px; }
  .quiz h2{ font-size: 16px; }
  .btn{ padding: 12px 12px; min-height: 50px; border-radius: 10px; }
  #next-btn{ width: 100%; border-radius: 10px; padding: 12px; }
}


@media (prefers-color-scheme: dark){
  :root{
    --card-bg: rgba(3,6,18,0.72);
    --muted: #9aa4b2;
    --accent: #60a5fa;
    --accent-2: #22d3ee;
    --shadow-1: 0 18px 50px rgba(2,6,23,0.7);
  }
  body{
    color: #e6eef8;
    background: linear-gradient(135deg, #020617 0%, #071033 100%);
  }
  .app{
    border: 1px solid rgba(255,255,255,0.04);
    box-shadow: 0 12px 40px rgba(2,6,23,0.7);
  }
  .btn{
    background: linear-gradient(180deg, rgba(255,255,255,0.02), rgba(255,255,255,0.01));
    border: 1px solid rgba(255,255,255,0.04);
    color: #e6eef8;
    box-shadow: none;
  }
  .btn.correct::after{ background: rgba(16,185,129,0.12); color: var(--success); }
  .btn.incorrect::after{ background: rgba(239,68,68,0.06); color: var(--danger); }
}