* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: sans-serif;
}

#centre-container {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

#box {
    width: 400px;
    height: 375px;

    display: flex;
    flex-direction: column;
    justify-content: space-evenly;

    border-radius: 1em;
    border: 1px solid rgba(255, 255, 255, 0.08);

    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
}

#num {
    font-size: 9em;
    font-weight: bold;
    text-align: center;
}

.buttons {
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
}

.btn {
    background-color: lightgray;
    font-size: 1em;
    font-weight: bold;

    padding: 0.7em 1.25em;

    border: none;
    border-radius: 8px;

    cursor: pointer;

    opacity: 0.75;
    transition: opacity 0.25s;
}

.btn:hover {
    opacity: 1;
}

.red {
    background-color: #e63946;
}
.reset {
    background-color: lightgray;
}
.blue {
    background-color: #1a6fb5;
}
.yellow {
    background-color: #e9a11a;
}
.green {
    background-color: #2a9d5c;
}