body {
    font-family: 'Segoe UI', Arial, sans-serif;
    background: linear-gradient(135deg, #e7f0fd 0%, #f7f7f7 100%);
    margin: 0;
    padding: 0;
}
.container {
    max-width: 420px;
    margin: 48px auto;
    background: #fff;
    padding: 32px 28px 28px 28px;
    border-radius: 16px;
    box-shadow: 0 4px 24px rgba(45,123,229,0.12);
    position: relative;
}
h1 {
    text-align: center;
    color: #2d7be5;
    font-size: 2.2em;
    margin-bottom: 8px;
    letter-spacing: 1px;
}
.level, .timer, .score, .highscore {
    text-align: center;
    margin-top: 10px;
    font-weight: 500;
    font-size: 1.1em;
}
.question {
    font-size: 1.5em;
    margin: 28px 0 18px 0;
    text-align: center;
    color: #1a2a3a;
    font-weight: 600;
    letter-spacing: 1px;
}
select, input[type="number"] {
    width: 100%;
    padding: 10px;
    font-size: 1.1em;
    margin-bottom: 16px;
    border: 1px solid #cfd8dc;
    border-radius: 6px;
    box-sizing: border-box;
    background: #f7f7f7;
    transition: border-color 0.2s;
}
select:focus, input[type="number"]:focus {
    border-color: #2d7be5;
    outline: none;
}
button {
    width: 100%;
    padding: 12px;
    background: linear-gradient(90deg, #2d7be5 60%, #4fc3f7 100%);
    color: #fff;
    border: none;
    border-radius: 6px;
    font-size: 1.1em;
    font-weight: 600;
    cursor: pointer;
    box-shadow: 0 2px 8px rgba(45,123,229,0.08);
    transition: background 0.2s;
}
button:hover {
    background: linear-gradient(90deg, #4fc3f7 0%, #2d7be5 100%);
}
.feedback {
    text-align: center;
    margin-top: 12px;
    font-size: 1.1em;
    font-weight: 500;
    color: #e52d2d;
    min-height: 24px;
    transition: color 0.2s;
}
.feedback:empty {
    min-height: 24px;
}
.timer {
    text-align: center;
    font-size: 1.15em;
    margin-top: 8px;
    color: #e52d2d;
    font-weight: 600;
}
.leaderboard {
    margin-top: 32px;
    background: #f7f7f7;
    border-radius: 8px;
    padding: 12px 0 8px 0;
    box-shadow: 0 1px 4px rgba(45,123,229,0.05);
}
.leaderboard h2 {
    text-align: center;
    color: #2d7be5;
    font-size: 1.2em;
    margin-bottom: 8px;
}
.leaderboard ul {
    list-style: none;
    padding: 0;
    margin: 0;
}
.leaderboard li {
    background: #e7f0fd;
    margin: 4px 0;
    padding: 8px 12px;
    border-radius: 4px;
    text-align: center;
    font-size: 1em;
    color: #1a2a3a;
    font-weight: 500;
}