html {
    box-sizing: border-box;
    font-size: 10px;
    background-image: linear-gradient(to left, #662d8c, #ed1e79);
}

*, *:before, *:after {
    box-sizing: inherit;
}

body {
    margin: 0;
    text-align: center;
    font-family: 'Inconsolata', monospace;
}

.display__time-left {
    font-weight: 100;
    font-size: 20rem;
    margin: 0;
    color: white;
    text-shadow: 4px 4px 0 rgba(0, 0, 0, 0.322);
}

.timer {
    display: flex;
    min-height: 100vh;
    flex-direction: column;
}

.timer__controls {
    display: flex;
}

.timer__controls > * {
    flex: 1;
}

.timer__controls form {
    flex: 1;
    display: flex;
}

.timer__controls input {
    flex: 1;
    border: 0;
    padding: 2rem;
}

.timer__button {
    background: none;
    border: 0;
    cursor: pointer;
    color: white;
    font-size: 2rem;
    text-transform: uppercase;
    background: rgba(0,0,0,0.1);
    border-bottom: 3px solid rgba(0,0,0,0.2);
    border-right: 1px solid rgba(0,0,0,0.2);
    padding: 1rem;
    font-family: 'Inconsolata', monospace;
}

.timer__button:hover,
.timer__button:focus {
    background: rgba(0,0,0,0.2);
    outline: 0;
}

.display {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.display__end-time {
    font-size: 4rem;
    color: white;
}

.gradient-1 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to bottom, #d4145a, #fbb03b);
    z-index: -1;
    transition: all 0.3s linear;
    opacity: 1;
}

.gradient-2 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to right, #662d8c, #1eeded);
    z-index: -1;
    transition: all 0.3s linear;
    opacity: 0;
}

.gradient-3 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to top, #02aabd, #00cdac);
    z-index: -1;
    transition: all 0.5s linear;
    opacity: 1;
}

.gradient-4 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to top left, #ea8d8d, #a890fe);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 0;
}
.gradient-5 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to top right, #2e3192, #1bffff);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 1;
}
.gradient-6 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to bottom left, #bff098, #6fd6ff);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 0;
}
.gradient-7 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
}
.gradient-8 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to bottom right, #764ba2, #667eea);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 0;
}
.gradient-9 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to left, #a1c4fd, #70c4eb);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 1;
}
.gradient-10 {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background-image: linear-gradient(to bottom, #18498a, #1dca51);
    z-index: -1;
    transition: opacity 0.5s linear;
    opacity: 0;
}