style.css

* {
    box-sizing: border-box;
}

img {
    width: 100%;
    height: 100%;
}

html,
body {
    overflow: clip;
    scrollbar-color: #000000 #ffffff;
    margin: 0;
    padding: 0;
    font-family: "Comic Sans MS", "Comic Sans", cursive;
}

body{
    background-color: black;
}

div {
    margin: 10px 0;
}

.content {
    width: 70%;
    margin: 0 15%;
}

.selectable {
    -webkit-touch-callout: all;
    -webkit-user-select: all;
    -khtml-user-select: all;
    -moz-user-select: all;
    -ms-user-select: all;
    user-select: all;
}

textarea,
input,
output {
    width: 100%;
    background: white;
    font-size: 16px;
    width: 100%;
    overflow-y: auto;
    resize: none;
    height: 200px;
    border: 10px groove grey;
    border-radius: 25px;
}

output {
    cursor: pointer;
    display: block;
    word-break: break-all;
    white-space: pre-wrap;
}

::placeholder {
    text-align: center;
    line-height: 200px;
    font-size: 50px;
    font-weight: bold;
}

button {
    cursor: pointer;
    width: 100%;
    font-size: 20px;
    font-family: "Comic Sans MS", "Comic Sans", cursive;
    appearance: none;
    border: .2em solid #ffffff;
    background-color: black;
    padding: .85em 1.5em;
    color: #ffffff;
    border-radius: 2em;
    z-index: 2;
    overflow: clip;
    position: relative;
    transition: 0.4s;
}

button:hover{
    color: black;
    border-color: grey;
}

button::before {
    position: absolute;
    content: "";
    top: 0;
    right: 0;
    bottom: 0;
    left: 50%;
    background-color: white;
    z-index: -1;
    transition: 0.35s;
    width: 0%;
}

button:hover:before {
    width: 100%;
    left: 0;
}

#circle {
    position: absolute;
    width: 0;
    height: 100%;
    background-color: lightpink;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
    border-radius: inherit;
    z-index: -1;
}