styles.css

* {
    padding: 0;
    margin: 0;
}

body {
    background: #666666;
    font-family: 'Mr De Haviland', cursive;
    text-align: center;
}

h1 {
    color: white;
    font-size: 100px;
    margin-top: 6%;
}

button {
    background: #77CCA4;
    outline: 0;
    border-radius: 100%;
    font-size: 50px;
    padding: 45px 58px;
    border: 0;
    color: #F0F0D8;
    margin-top: 50px;
    cursor: pointer;
    transition: all 0.3s ease-in;
}

button:hover,
button:focus {
    transform: scale(1.1);
}

button.animate {
    animation: voice_detected 2s infinite;
}

@keyframes voice_detected {
    0%, 80% {
        box-shadow: 0px 0px 0px 0px #b4debe;
    }

    20%, 60% {
        box-shadow: 0px 0px 0px 34px #b4debe;
    }

    40% {
        box-shadow: 0px 0px 0px 10px #B4DEBE;
    }
}

.messages {
    font-size: 40px;
    text-align: left;
    display: flex;
    flex-direction: column;
    margin-left: 30%;
    margin-top: 6%;
    color: #F0F0D8;
}

@media only screen and (max-width: 768px) {
    h1 {
        font-size: 45px;
        margin-top: 7%;
    }

    button {
        font-size: 40px;
        padding: 37px 48px;
        transform: translateX(-50%) translateY(-50%);
        position: absolute;
        left: 50%;
        top: 50%;
        margin: 0;
    }

    button:hover,
    button:focus {
        transform: translateX(-50%) translateY(-50%) scale(1.1);
    }

    .messages {
        position: absolute;
        bottom: 7%;
        font-size: 27px;
        margin-left: 12%;
        margin-top: 29%;
    }
}