body {
    position: relative;
    width: 100vw;
    height: 100vh;
    margin: 0;
    padding: 0;
}

header {
    position: relative;
    width: 100%;
    height: 30%;
    display: flex;
    justify-content: center;
    align-items: flex-end;
}

header > img {
    position: relative;
    width: auto;
    height: 70%;
}

main {
    position: relative;
    width: 100%;
    height: 65%;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.btn-area {
    position: relative;
    width: 40%;
    height: 35%;
    display: flex;
    justify-content: space-evenly;
    align-items: center;
}

.btn-area > button {
    position: relative;
    width: 45%;
    height: 3.5em;
    outline: none;
    border: none;
    border-radius: 50px;
    box-shadow: 1px 1px 3px rgba(100, 100, 100, 0.6);
    background-image: linear-gradient(to bottom, rgb(240, 240, 240), rgb(210, 210, 210));
    letter-spacing: 0.1em;
    padding-left: 0.1em;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
}

.btn-area > button#main {
    width: 60%;
    height: 5em;
    color: rgb(255, 255, 255);
    background-image: linear-gradient(to bottom, rgb(248, 129, 227), rgb(160, 53, 141));
}

button#top {
    position: relative;
    width: 10%;
    height: 2em;
    font-size: 0.9em;
    outline: none;
    border: none;
    border-radius: 10px;
    background-image: linear-gradient(to bottom, rgb(250, 250, 250), rgb(230, 230, 230));
    box-shadow: 1px 1px 3px rgba(100, 100, 100, 0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
}

.btn-area > button:active, button#top:active {
    position: relative;
    top: 2px;
}

div#error {
    position: absolute;
    left: 50%;
    bottom: 0.5em;
    transform: translateX(-50%);
    color: rgb(255, 0, 0);
}

footer {
    position: relative;
    width: 100%;
    height: 5%;
    color: rgb(255, 255, 255);
    background-color: rgb(164, 164, 165);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 0.9em;
}