body {
    margin: 0;
    min-height: 100vh;
    overflow-y: auto;
    background: #0f2418;
    color: white;
    font-family: Arial, sans-serif;
}

.page {
    max-width: 640px;
    margin: 0 auto;
    padding: 16px 16px 40px;
    box-sizing: border-box;
}

.top-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 18px;
}

.nav-btn,
.go-btn {
    border: none;
    border-radius: 8px;
    color: white;
    cursor: pointer;
    font-weight: bold;
    text-decoration: none;
    text-align: center;
}

.nav-btn {
    display: inline-block;
    padding: 10px 14px;
    background: #FF0000;
    font-size: 16px;
}

.nav-btn.home {
    background: #2a6fad;
}

.nav-btn.math {
    background: #2ECC40;
}

.go-btn {
    margin-top: 12px;
    padding: 14px 28px;
    background: #2ECC40;
    font-size: 22px;
}

.panel {
    background: rgba(20, 20, 20, 0.92);
    border-radius: 16px;
    padding: 20px;
    text-align: center;
}

h1 {
    color: #FFD100;
    margin: 0 0 10px;
}

.best {
    color: #FFD100;
    font-weight: bold;
}

.hud {
    display: flex;
    justify-content: space-between;
    font-size: 22px;
    font-weight: bold;
}

#hearts {
    color: #ff4d4d;
}

#timer-wrap {
    height: 14px;
    margin: 14px 0 8px;
    background: #333;
    border-radius: 8px;
    overflow: hidden;
}

#timer-bar {
    height: 100%;
    width: 100%;
    background: #FFD100;
}

#question {
    font-size: 42px;
    font-weight: bold;
    margin: 20px 0;
}

#answers {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
}

#answers button {
    padding: 16px;
    font-size: 24px;
    font-weight: bold;
    border: none;
    border-radius: 10px;
    background: #2a6fad;
    color: white;
    cursor: pointer;
}

#answers button:disabled {
    cursor: default;
}

#answers button.right {
    background: #2ECC40;
}

#answers button.wrong {
    background: #CC0000;
}

#play-note {
    min-height: 24px;
    font-size: 20px;
}