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

:root {
    --roundedCorner: 5px;
    --font: 'PT Sans', sans-serif;
    --displayBackground: #455a64;
    --numbersBackground: #1c313a;
    --operatorsBackground: #006978;
    --clearBackground: #d32f2f;
    --digitColor: #FFFFFF;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

main {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 30vw;
    height: 65vh;
    border: 1px solid black;
    border-radius: var(--roundedCorner);
    background-color: var(--numbersBackground);
}

#display {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    min-height: 10vh;
    min-width: 27vw;
    margin-bottom: 0.75rem;
    padding-right: 0.5rem;
    border-radius: var(--roundedCorner);
    font-family: var(--font);
    font-size: 3rem;
    background-color: var(--displayBackground);
    color: var(--digitColor);
}
#pad {
    display: grid;
    grid-template-columns: repeat(4, 25%);
    grid-template-rows: repeat(4, 20%);
    min-height: 50vh;
    min-width: 27vw;
    background-color: var(--numbersBackground);
}

.btnPad {
    margin: 0.1rem;
    border:none;
    border-radius: var(--roundedCorner);
    font-family: var(--font);
    font-size: 1.5rem;
    background-color: var(--numbersBackground);
    color: var(--digitColor);
}

.shadowWhite:hover {
    box-shadow: 0.5px 0.5px 4px 2px rgba(113,135,146,0.8);
}

.shadowWhite:active {
    transform: scale(0.90);
    box-shadow: 5px 5px 15px 1px rgba(113,135,146,0.25);
}

.op.btnPad {
    background-color: var(--operatorsBackground);
}

.op:hover {
    box-shadow: 0.5px 0.5px 4px 2px rgba(86,200,213,0.8);
}

.op:active {
    transform: scale(0.90);
    box-shadow: 5px 5px 15px 1px rgba(86,200,213,0.25);
}

#cancel.btnPad {
    background-color: var(--clearBackground);
}

#cancel:hover {
    box-shadow: 0.5px 0.5px 4px 2px rgba(255,102,89,0.8);
}

#cancel:active {
    transform: scale(0.90);
    box-shadow: 5px 5px 15px 1px rgba(255,102,89,0.25);
}