* {
    box-sizing: border-box;
}

button {
    height: 100px;
    background-color: rgb(219, 215, 215);
    border-color: rgb(219, 215, 215);
    font-size:x-large;
    font-weight: 550;
    border: 2px solid black;
}

button:hover {
    filter: brightness(1.15);
}

button:active{
    filter: brightness(.75);
}

.output {
    grid-area: output;
    display: flex;
    align-items: center;
    justify-content: right;
    font-family:monospace;
    background-color: black;
    color: white;
}

.clear {
    grid-area: clear;
    border-left: 0;
}

.backspace {
    grid-area: backspace;
}

.actions {
    display: grid;
    grid-template-areas:
    "clear backspace";
    grid-template-columns: 2fr 1fr;
}

.operands {
    display: grid;
    width: 100%;
    grid-area: operands;
}

.operand {
    background-color: orange;
    color: white;
    border-right: 0;
}

.equal {
    border-bottom: 0;
}

.numbers {
    display: grid;
    width: 100%;
    grid-template-columns: 1fr 1fr 1fr;
    grid-template-rows: 1fr 1fr 1fr 1fr;
}

.numbers button:nth-child(3n+1) {
    border-left: 0;
}

.zero {
    grid-column-start: 1;
    grid-column-end: 4;
    border-bottom: 0;
}

.calculator {
    display: grid;
    width: 400px;
    height: 600px;
    font-family:Arial, Helvetica, sans-serif;
    font-size:x-large;
    grid-template-areas:
    "output output"
    "actions operands"
    "numbers operands";
    grid-template-columns: 3fr 1fr;
    grid-template-rows: 1fr 1fr 4fr;
    margin: 0%;
}