:root {
    --display-color: #222;
    --symbols-color: #a39a9a;
    --symbols-hover-color: #797272;
    --numbers-color: #d8dbe0;
    --numbers-hover-color: #b2b5b9;
    --equals-color: #ffa500;
    --equals-hover-color: #e29a13;
}

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;

    font-family: 'Courier New', Courier, monospace;

    color: #fff;
    background-color: #969191;
    height: 100vh;
    padding: 0.5rem;
}

/* Calculator styling */
#calculator {
    width: 400px;
    border-radius: 14px;
    overflow: hidden;
    box-shadow: rgba(0, 0, 0, 0.35) 0px 5px 15px;
}

#operation-display {
    font-size: 50px;

    background-color: var(--display-color);
    height: 140px;
    width: 100%;

    overflow-y: scroll;
    word-wrap: break-word;
    hyphens: none;

    padding: 0.5rem;
}

#result-display {
    display: none;
    font-size: 20px;

    background-color: var(--display-color);

    overflow-y: scroll;
    word-wrap: break-word;
    hyphens: none;

    padding: 0.5rem;
}

/* Buttons */
button {
    font-size: 20px;
    font-weight: 600;

    height: 80px;
    border: none;

    cursor: pointer;
}

#top-row button {
    background-color: var(--symbols-color);
}

#top-row > button:hover {
    background-color: var(--symbols-hover-color);
}

#bottom-row > #main-grid > button {
    background-color: var(--numbers-color);
}

#bottom-row > #main-grid > button:hover {
    background-color: var(--numbers-hover-color);
}

#equals {
    background-color: var(--equals-color);
    height: 100%;
}

#equals:hover {
    background-color: var(--equals-hover-color);
    height: 100%;
}

/* Sections */
#top-row,
#bottom-row {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
}

#bottom-row > #main-grid {
    grid-column: span 3;
}

#bottom-row > #main-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
}