:root{
  --bg: #f7f8fa;
  --white: #ffffff;
  --black: #111;
  --yellow: #ffd34d;   /* logo yellow */
  --green: #2db35b;    /* start button / accent green */
  --purple: #6b3fb6;   /* streak block purple */
  --muted: #666;
  --card-radius: 14px;
  --max-width: 460px;
}

*{box-sizing:border-box;font-family: "Helvetica Neue", Arial, sans-serif}

body{
  margin:0;
  background:var(--bg);
  color:var(--black);
  display:flex;
  align-items:flex-start;
  justify-content:center;
  padding:28px 16px;
  min-height:100vh;
}

.app{
  width:100%;
  max-width:var(--max-width);
}

/* logo block */
.logo-block{
  background:var(--yellow);
  border-radius:var(--card-radius);
  padding:28px 18px;
  text-align:center;
  box-shadow:0 6px 18px rgba(0,0,0,0.06);
  margin-bottom:18px;
}

.logo-text{
  font-size:48px;
  font-weight:800;
  letter-spacing:1px;
  color: #0d0d0d;
  line-height:1;
}

.logo-sub{
  font-size:18px;
  color: #0d0d0d;
  margin-top:8px;
  opacity:0.95;
}

/* controls */
.controls{
  display:flex;
  justify-content:center;
  margin-bottom:18px;
}
.btn{
  display:inline-block;
  padding:12px 18px;
  border-radius:10px;
  border:1px solid rgba(0,0,0,0.06);
  background:var(--white);
  cursor:pointer;
  font-size:16px;
}
.btn:active{transform:translateY(1px)}
.btn-green{
  background:var(--green);
  color:#fff;
  border:none;
  box-shadow: 0 6px 16px rgba(45,179,91,0.14);
  font-weight:700;
}

/* streak block */
.streak-block{
  margin-top:8px;
  background:var(--purple);
  color:#fff;
  padding:18px;
  border-radius:14px;
  text-align:center;
  box-shadow:0 6px 16px rgba(107,63,182,0.12);
  margin-bottom:22px;
}

.streak-title{font-size:14px; opacity:0.95}
.streak-count{font-size:22px; font-weight:700; margin-top:6px}

/* quiz area */
.hidden{display:none}
.question-header{font-size:14px; color:var(--muted); margin-bottom:6px}
.question-text{font-size:20px; margin:6px 0 14px 0; font-weight:600}

.answers{display:flex;flex-direction:column;gap:10px}
.answer{
  background:var(--white);
  padding:12px 14px;
  border-radius:10px;
  border:2px solid rgba(0,0,0,0.06);
  cursor:pointer;
  text-align:left;
  font-size:16px;
}
.answer.correct{background: #e6fbef; border-color: #2db35b}
.answer.wrong{background:#fff0f0; border-color:#e05b5b; opacity:0.98}
.answer.disabled{cursor:default; opacity:0.9}

.nav{display:flex;justify-content:flex-end;margin-top:12px}
.btn-next{background:var(--black); color:#fff; border:none; padding:10px 14px; border-radius:8px}
.btn[disabled]{opacity:0.5; cursor:not-allowed}

/* result area */
.result-area{text-align:center;padding:18px;background:var(--white);border-radius:12px;margin-top:18px;box-shadow:0 6px 12px rgba(0,0,0,0.05)}
.result-area h2{font-size:22px;margin:6px 0 12px 0}
.result-area .btn{margin-top:8px}

/* responsive tweaks */
@media (max-width:420px){
  .logo-text{font-size:40px}
  .logo-block{padding:20px}
}