$device-s-width: 640px;
$device-m-width: 1200px;

// Normalize

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

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

    font-family: 'Lato', sans-serif;
    font-weight: 300;
    font-size: 20px;

    line-height: 1;
}

textarea {
    border: none;
    outline: gray;

    width: 100%;

    padding: 1rem;

    box-shadow: -2px 4px 8px 1px #00000020, -1px 1px 1px 0px #00000010;
    border-radius: 0.25rem;
    background: #ffffff;
}

label {
    font-weight: 400;
}

input[type='text'] {
    border: none;
    outline: gray;

    width: 100%;

    padding: 0.5rem;

    box-shadow: -2px 4px 4px 0 #00000020;
    border-radius: 0.25rem;
    background: #ffffff;

    font-family: 'Lato';
    font-weight: 400;
    font-size: 18px;
    color: #555;
}

button {
    cursor: pointer;

    font-family: 'Lato';
    font-weight: 600;
    font-size: 18px;
    color: #555;

    border: 1px solid #c8c8c8;
    padding: 0.5rem 2rem;

    box-shadow: -2px 4px 16px 0 #00000010, -2px 4px 4px 0 #00000010;
    border-radius: 0.25rem;

    background: linear-gradient(180deg, #f0f0f0, #dfdfdf 20%, #d8d8d8 80%, #c0c0c0);

    transition: all 100ms ease-in;

    &:hover {
        border: 1px solid #c4c4c4;
        box-shadow: -2px 4px 20px 4px #00000010, -2px 4px 6px 2px #00000010;
        background: linear-gradient(180deg, #f8f8f8, #e4e4e4 20%, #e4e4e4 80%, #c8c8c8);
    }
}

.link,
a,
a:visited {
    cursor: pointer;

    color: #3a9999;
    text-decoration: none;

    &:hover {
        text-decoration: underline;
    }
}

// Typography

p {
    margin: 0;
}

p + p {
    margin-top: 0.5rem;
}

$base-font-size: 16px;
$heading-scale: 1.25;

@function pow($number, $exponent) {
    $value: 1;

    @if $exponent > 0 {
        @for $i from 1 through $exponent {
            $value: $value * $number;
        }
    }

    @return $value;
}

@for $i from 1 through 4 {
    h#{$i} {
        margin: 0;

        $factor: pow($heading-scale, 4 - $i);
        font-size: $base-font-size * $factor;
        font-weight: 500;

        &:not(:first-child) {
            padding-top: 0.5rem * $factor;
        }

        line-height: 1;
    }
}

//
// Components
//

.text-body {
    font-family: 'EB Garamond', serif;
    font-weight: 400;
    font-size: 21px;

    line-height: 1.41;

    b,
    strong {
        font-weight: 600;
    }
}

//
// Structure
//

body {
    display: flex;
    flex-direction: column;
    align-items: center;

    background: #f8f8f8;
}

main {
    padding: 2rem 2rem 6rem;
    width: 100%;

    display: flex;
    flex-direction: column;
    align-items: center;

    gap: 2rem;

    .logo {
        // font-size: 42px;
        // font-family: 'EB Garamond';
        // font-weight: 600;
        font-size: 38px;
        font-family: 'Lato';
        font-weight: 300;
    }

    .subtitle {
        font-size: 24px;
    }
}

main.home {
    .board {
        width: 100%;

        display: grid;
        grid-template-columns: repeat(auto-fill, minmax(60ch, 1fr));
        gap: 2rem;
    }
}

//
// Components
//

main {
    .problem {
        padding: 1rem;
        // border: 1px solid #ddd;

        box-shadow: -2px 4px 8px 1px #00000020, -1px 1px 1px 0px #00000010;
        border-radius: 0.5rem;
        background: #ffffff;

        display: grid;
        grid-template-rows: auto 1fr;
        gap: 0.5rem;

        max-width: 80ch;

        .problem-header {
            display: grid;
            grid-template-columns: auto;

            .problem-title {
                font-size: 24px;
                font-weight: 700;
            }
        }

        .problem-content {
            @extend .text-body;
        }
    }

    .solution-editor {
        display: grid;
        width: 100%;
        grid-template-columns: repeat(2, 1fr);

        gap: 1rem;

        .editor,
        .preview {
            width: 100%;
            max-width: 70ch;

            display: flex;
            flex-direction: column;
            align-items: center;

            gap: 1rem;
        }

        .editor {
            justify-self: end;

            textarea {
                font-family: 'DM Mono', monospace;
                font-size: 18px;

                resize: none;
                overflow-y: hidden;

                min-height: 8rem;
            }
        }

        .preview {
            justify-self: start;

            .placeholder {
                color: #444;
            }

            .preview-content {
                @extend .text-body;

                width: 100%;

                padding: 1rem;

                box-shadow: -2px 4px 8px 1px #00000020, -1px 1px 1px 0px #00000010;
                border-radius: 0.25rem;
                background: #ffffff;
            }
        }
    }

    .form {
        min-width: 50ch;

        display: grid;
        grid-template-columns: auto 1fr;

        // border: 2px solid #ccc;
        border-radius: 1rem;

        box-shadow: -2px 4px 16px 4px #00000018, -2px 4px 4px 1px #00000018;

        padding: 1.5rem 2rem 1rem;
        gap: 1rem;

        align-items: center;

        .fill {
            grid-column: span 2;
            justify-self: center;
        }
    }
}

.math-inline {
    font-size: 95%;
}

//
// Mobile
//

// Not on mobile
@media screen and (min-width: $device-s-width) and (pointer: fine) {
    // ...
}

// On mobile
@media screen and (max-width: $device-s-width), (pointer: coarse) {
    main {
        .solution-editor {
            grid-template-columns: auto;
            grid-template-rows: auto auto;
        }
    }
}

@media screen and (max-width: $device-m-width), (pointer: coarse) {
    main {
        .solution-editor {
            grid-template-columns: auto;
            grid-template-rows: auto auto;

            .preview,
            .editor {
                justify-self: center;
            }
        }
    }
}