style.css

* {
    font-family: cursive;
}

body {
    margin: 0;
    padding: 0;
    text-align: center;
    background: #000;
    margin-top: 1rem;
}

/* Score section */
.score {
    background-color: plum;
    width: 70%;
    max-width: 400px;
    border-radius: 1.5rem;
    margin: auto;
    box-sizing: border-box;
    padding: 1rem;
    margin-top: 3rem;
}

h1 {
    font-size: 1.5rem;
}

#highest-score {
    font-size: 1rem;
    color: rgb(97, 30, 97);
}

/* Game container */
.container {
    display: flex;
    justify-content: center;
    width: 70%;
    max-width: 400px;
    margin: auto;
    border-radius: 2rem;
}

/* Buttons */
.btn {
    width: 120px;
    height: 120px;
    border-radius: 15%;
    margin: 1rem;
    box-shadow: rgba(17, 17, 26, 0.1) 0px 8px 24px, rgba(17, 17, 26, 0.1) 0px 16px 56px, rgba(17, 17, 26, 0.1) 0px 24px 80px;
    background-color: rgb(254, 130, 130);
    border: 2px solid rgb(206, 49, 49);
}

.yellow {
    background-color: rgb(148, 148, 246);
    border: 2px solid blue;
}

.green {
    background-color: rgb(98, 241, 181);
    border: 2px solid rgb(41, 97, 116);
}

.blue {
    background-color: rgb(208, 146, 190);
    border: 2px solid rgb(158, 27, 97);
}

/* Flashing effect */
.flash {
    background: rgb(236, 232, 241);
}

.userflash {
    background-color: rgb(88, 41, 197);
}

/* Start and Restart buttons */
.start,
.restart {
    margin-top: 1rem;
    background-color: rgb(77, 72, 72);
    width: 8rem;
    height: 3rem;
    border-radius: 3rem;
    border: none;
    color: white;
}

/* Responsive media queries */
@media (max-width: 500px) {
    .container {
        width: 80%;
        max-width: 300px;
    }

    .btn {
        width: 80px;
        height: 100px;
        border-radius: 15%;
        margin: 0.5rem;
    }
}