.prime-prompt {
    font-size: 1.15rem;
    font-weight: 600;
    color: #444;
    text-align: center;
    margin: 0.5rem 0 1.25rem;
}

.prime-number-box {
    width: 6.5rem;
    margin: 0 auto 1.25rem;
    padding: 0.9rem 0;
    font-size: 2.2rem;
    font-weight: 800;
    text-align: center;
    color: #1f3a5f;
    background: #eef5ff;
    border: 2px solid #bcd4f6;
    border-radius: 18px;
}

.prime-options {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.prime-option {
    min-width: 5.5rem;
    padding: 0.85rem 1.2rem;
    font-size: 1.3rem;
    font-weight: 700;
    color: #1f3a5f;
    background: #ffffff;
    border: 2px solid #bcd4f6;
    border-radius: 14px;
    cursor: pointer;
    transition: transform 0.1s ease, box-shadow 0.1s ease;
}

.prime-option:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(31, 58, 95, 0.15);
}

.prime-hint {
    text-align: left;
}

.prime-hint p {
    margin: 0.35rem 0;
}