styles.css

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

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
    transition: all 0.2s ease;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: #fefefe;
    padding: 0 10px;
    flex-direction: column;
}

.wrapper {
    background: #121212;
    width: 1100px;
    border-radius: 24px;
    padding: 36px 42px;
}

.wrapper header {
    color: #dadada;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

header h2 {
    font-size: 1.6rem;
    user-select: none;
}

header .column {
    display: flex;
    align-items: center;
}

header .column span {
    font-weight: 500;
    font-size: 1.2rem;
    margin-right: 16px;
}

.volume-slider input {
    accent-color: #fff;
    outline: none;
}

.keys-checkbox input {
    appearance: none;
    background: #2e2e2e;
    width: 64px;
    height: 32px;
    border-radius: 32px;
    position: relative;
    cursor: pointer;
}

.keys-checkbox input::before {
    content: "";
    height: 24px;
    width: 24px;
    left: 5px;
    border-radius: inherit;
    background: #ababab;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    transition: all 0.2s ease;
}

.keys-checkbox input:checked::before {
    left: 35px;
    background: #fff;
}

.piano-keys {
    display: flex;
    margin-top: 36px;
}

.piano-keys .key {
    list-style: none;
    color: #b0b0b0;
    position: relative;
    text-transform: uppercase;
    cursor: pointer;
    user-select: none;
}

.piano-keys .white {
    width: 60px;
    height: 240px;
    border-radius: 8px;
    background: linear-gradient(#fff 96%, #ddd 4%);
    border: 1px solid #000;
}

.piano-keys .white.active {
    background: linear-gradient(to bottom, #fff 0%, #ddd 100%);
    box-shadow: inset -4px 4px 24px rgba(0, 0, 0, 0.14);
}

.piano-keys .black {
    width: 44px;
    height: 140px;
    border-radius: 0 0 6px 6px;
    margin: 0 -22px 0 -22px;
    z-index: 2;
    background: linear-gradient(#2b2b2b, #000);
}

.piano-keys .black.active {
    background: linear-gradient(to bottom, #000, #2b2b2b);
    box-shadow: inset -4px 4px 14px rgba(255, 255, 255, 0.06);
}

.piano-keys span {
    position: absolute;
    bottom: 24px;
    width: 100%;
    text-align: center;
    font-size: 1.14rem;
}

.piano-keys .key.hide span {
    display: none;
}

#hint {
    margin-top: 2%;
    color: #ffffff;
}

#hint:hover {
    color: #000000;
}