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

body {
    min-height: 100vh;
    font-family: 'Roboto', sans-serif;
    background-color: var(--bg-background);
}

:root {
    font-size: 62.5%;

    --fc-timer: #323238;
    --bg-card: #E1E1E6;
    --bg-cardHover: #C9C9C9;
    --bg-cardSelected: #02799D;
    --bg-cardSelectedHover: #006483;
    --bg-body: #FFF;
    --bg-background: var(--bg-body);
}

.dark:root {
    font-size: 62.5%;

    --fc-timer: #FFF;
    --bg-card: #29292E;
    --bg-cardHover: #39393f;
    --bg-cardSelected: #0A3442;
    --bg-cardSelectedHover: #0d4253;
    --bg-body: #FFF;
    --bg-background: #121214;
    --bg-gray: #C4C4CC;
}

nav {
    display: flex;
    justify-content: end;
    margin: 20px;
}

nav svg {
    cursor: pointer;
}

.hide {
    display: none;
}

main {
    display: grid;
    grid-template-columns: 1fr 1fr;
    place-items: center;
    height: 80vh;
}

#timer {
    font-size: 126px;
    margin-bottom: 3.0rem;
    color: var(--fc-timer);
}

#controls {
    display: flex;
    gap: 4.0rem;
}

.dark #controls svg path {
    fill: var(--bg-gray);
}

button {
    border: none;
    background: none;
    cursor: pointer;
}

#card-sounds {
    display: grid;
    gap: 3.2rem;
    grid-template-columns: 1fr 1fr;
}

#card-sounds > div {
    width: 138px;
    height: 152px;
    border-radius: 2.4rem;
    background-color: var(--bg-card);
    cursor: pointer;
}

#card-sounds svg {
    margin-top: 2.4rem;
    margin-left: 4.0rem;
}

#card-sounds svg path {
    fill: var(--fc-timer);
}

.dark #card-sounds svg path {
    fill: var(--bg-gray);
}

#card-sounds .icon-white svg path {
    fill: var(--bg-body);
}

#card-sounds .icon-white #volume {
    background: var(--bg-body);
}

#card-sounds .icon-white #volume::-webkit-slider-thumb {
    background: var(--bg-body);
}

#volume {
    background: var(--fc-timer);
    -webkit-appearance: none;
    outline: none;
    margin-left: 2.4rem;
    margin-top: 3.4rem;
    width: 9.0rem;
    height: .4rem;
    border-radius: .5rem;
}

#volume::-webkit-slider-thumb {
    -webkit-appearance: none; 
    appearance: none;
    width: 1.6rem;
    height: 1.6rem; 
    background: var(--fc-timer);
    cursor: pointer; 
    border-radius: 100%;
}

@media (max-width: 768px) {
    main {
        grid-template-columns: 1fr; 
    }

    #controls {
        justify-content: center;
    }
}