style.css

* {
    box-sizing: border-box;
}

html, body {
    height: 100%;
    width: 100%;
    margin: 0;
}

.app-container {
    height: 100%;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}

.stopwatch {
    width: 80%;
    padding: 5px;
    border-radius: 10px;
    border: 5px solid #ff5500;

    display: grid;
    justify-items: center;
    grid-column-gap: 10px;
    grid-row-gap: 5px;
    grid-template-areas:
	"timer timer timer"
	"reset stop start";
}

.stopwatch .timer {
    grid-area: timer;
    font-size: 2em;
}

.stopwatch .start {
    grid-area: start;
    font-size: 1.2em;
}

.stopwatch .stop {
    grid-area: stop;
    font-size: 1.2em;
}

.stopwatch .reset {
    grid-area: reset;
    font-size: 1.2em;
}