* {
    margin: 0;
    padding: 0;
    z-index: 1;
    position: relative;
    box-sizing: border-box;
    font-size: 16px;
}

:root {
    --body-background-light: #E8E8E8;
    --body-background-dark: #E8EBD8;

    --title-color: #6C733D;
    --text-color: #202426;
    --footer-color: #202426;

    --button-background-light: #C1CC72;
    --button-background-dark: #9DA65D;
    --button-shadow: rgba(0, 0, 0, 0.26);
    --button-color: #202426;

    --box-background: #F2F2F2;
    --box-shadow: rgba(0, 0, 0, 0.16);
    --box-color: #202426;
    --check-background: #FFFFFF;
    --check-border: #707070;
}

@media (prefers-color-scheme: dark) {
    :root {
        --body-background-light: #262522;
        --body-background-dark: #0D0C0A;

        --title-color: #9DA65D;
        --text-color: #A6A6A6;
        --footer-color: #8C8C88;

        --button-background-light: #BFCC62;
        --button-background-dark: #9DA65D;
        --button-shadow: #8C8C88;
        --button-color: #202426;

        --box-background: rgba(32, 36, 38, 0.20);
        --box-shadow: rgba(0, 0, 0, 0.16);
        --box-color: #8C8C88;
        --check-background: #262626;
        --check-border: #707070;
    }
}

body {
    background: var(--body-background-light)
        linear-gradient(
            150deg,
            var(--body-background-dark),
            var(--body-background-light)
        );
    min-height: 100vh;
}

header {
    height: 6rem;
    margin: 0 auto;
    max-width: 920px;
    width: 80vw;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    flex-wrap: wrap;
}

header h1 {
    font-size: 3.25rem;
    font-weight: 200;
    font-family: 'Ubuntu', sans-serif;
    color: var(--title-color);
}

header nav button {
    padding: 0.075rem 0.625rem 0.125rem 0.625rem;
    font-size: 1.375rem;
    font-weight: 800;
    font-family: 'Noto Sans KR', sans-serif;
    color: var(--button-color);
    border: none;
    box-shadow: 0 0 0.375rem var(--button-shadow) inset;
}

header nav button:hover, header nav button:focus {
    filter: brightness(1.2);
    box-shadow: 0 0 0.5rem var(--button-shadow) inset;
}

header nav button:active {
    transform: scaleX(0.98) scaleY(0.98);
}

header nav button:first-child {
    margin-right: 1rem;
    background: var(--button-background-light);
    border-top-left-radius: 1rem;
}

header nav button:last-child {
    background: var(--button-background-dark);
    border-bottom-right-radius: 1rem;
}

div.content {
    margin: 2.85rem auto;
    padding-bottom: 4rem;
    max-width: 920px;
    width: 80vw;
    display: flex;
    flex-flow: wrap;
    justify-content: left;
    align-content: flex-start;
}

footer {
    width: 100%;
    position: absolute;
    bottom: 0.625rem;
    color: var(--footer-color);
    font-size: 1rem;
    font-weight: 500;
    font-family: 'Ubuntu', sans-serif;
    text-align: center;
}

@media (max-width: 640px) {
    div.content {
        width: unset;
        justify-content: center;
    }
    footer {
        position: relative;
    }
}