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

* {
    margin: 0;
}

:root {
    @media (prefers-reduced-motion: no-preference) {
        scroll-behavior: smooth;
    }
    overflow-y: scroll;
    color-scheme: light dark;
    --bold: 600;
    --highlight: orange;

    /* light mode (default) */
    --body-bg: #fff;
    --body-fg: #000;
    --el-bg: #ccc;
    --link-blue: blue;
    --loader: #ccc;
}

.darkmode {
    --body-bg: #000;
    --body-fg: #fff;
    --el-bg: #484848;
    --link-blue: aqua;
    --loader: #333;
}

:focus-visible {
    outline: 0.125rem solid orange;
    outline-offset: 0.1875rem;
}

body {
    background-color: var(--body-bg);
    @media (prefers-reduced-motion: no-preference) {
        transition: background-color 250ms linear;
    }
    color: var(--body-fg);
    font-family: system-ui;
    font-size: clamp(1rem, 0.8995rem + 0.4673vw, 1.25rem);
    min-height: 100vh;
    min-height: 100dvh;
    display: grid;
    grid-template-rows: auto 1fr auto;
    position: relative;
    line-height: 1.5;
}

.flow > * + * {
    margin-block-start: 1em;
    /* em NOT rem & margin-top NOT margin bottom */
}

strong,
b {
    font-weight: var(--bold);
}

h1,
h2,
p {
    text-wrap: balance;
}

h1 {
    font-size: clamp(1.375rem, 1.2745rem + 0.4673vw, 1.625rem);
    text-align: center;
    text-box: trim-both cap alphabetic;
}

h2 {
    font-size: clamp(1.125rem, 1.0245rem + 0.4673vw, 1.375rem);
}

h1,
h2 {
    font-weight: var(--bold);
}

kbd {
    background-color: #eee;
    border-radius: 0.1875rem;
    border: 0.0625rem solid #b4b4b4;
    box-shadow:
        0 0.0625rem 0.0625rem rgba(0, 0, 0, 0.2),
        0 0.125rem 0 0 rgba(255, 255, 255, 0.7) inset;
    color: black;
    display: inline-block;
    font-size: 0.85em;
    font-weight: 700;
    line-height: 1;
    padding: 0.125rem 0.25rem;
    white-space: nowrap;
}

a {
    color: var(--link-blue);
    text-decoration: none;
    text-underline-offset: 0.1875rem;

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

.external-link {
    color: var(--link-blue);
    text-underline-offset: 0.5em;
    text-decoration: none;

    &::after {
        color: var(--link-blue);
        content: " \27F6";
    }

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

.main-content,
.page-footer {
    padding-block: 1.5em;
}

.main-content {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    & .tab-info {
        text-align: center;
    }
}

.page-header,
.page-footer {
    border-style: solid;
    border-color: var(--body-fg);
}

.page-header {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    padding-block: 3rem 2.5rem;
    border-width: 0 0 0.0625rem 0;

    .title-link {
        display: flex;
        flex-wrap: wrap;
        gap: clamp(1rem, 0.5981rem + 1.8692vw, 2rem);
        justify-content: center;
        align-items: center;
        padding-inline: 1rem;
        margin-inline: auto;
        line-height: 1;
    }

    & p {
        text-align: center;
        max-width: 90%;
        margin-inline: auto;
    }

    & .not-supported {
        border: 5px solid var(--highlight);
        padding: 1rem;
    }

    @supports ((reading-flow: grid-rows) and (reading-flow: grid-columns)) {
        & .not-supported {
            display: none;
        }
    }
}

.page-footer {
    border-width: 0.0625rem 0 0 0;
}

.accordion {
    width: clamp(18.75rem, 11.215rem + 35.0467vw, 37.5rem);
    margin-inline: auto;
    & h2 {
        display: inline;
    }
    & details {
        overflow: clip;
    }

    & summary {
        cursor: pointer;
    }

    & p {
        text-wrap: pretty;
    }

    .note {
        border: 0.0625rem solid var(--body-fg);
        padding: 0.5em;
    }
}
@media (prefers-reduced-motion: no-preference) {
    @supports (interpolate-size: allow-keywords) {
        :root {
            interpolate-size: allow-keywords;
        }

        details {
            transition: height 0.5s ease;
            height: 2rem;

            &[open] {
                height: auto;
                overflow: clip;
            }
        }
    }
}

.forms {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: clamp(0.5rem, -0.1028rem + 2.8037vw, 2rem);

    & legend {
        font-weight: var(--bold);
        margin-inline-start: -0.25rem;
    }

    & fieldset {
        border: 0;
        padding: 0;
    }

    & .radios {
        display: flex;
        gap: clamp(0.5rem, 0.2991rem + 0.9346vw, 1rem);
    }

    & input[type="radio"] {
        transform: scale(1.25);
        accent-color: var(--link-blue);
    }
}

.grid-wrapper {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    width: fit-content;
    margin-inline: auto;

    & h2 {
        padding-block-end: 0.3125rem;
    }

    &:has(.grid-0) {
        & .reading-flow-type {
            font-family: system-ui, sans-serif;
        }
    }
}

.grid {
    display: grid;
    width: clamp(18.75rem, 11.215rem + 35.0467vw, 37.5rem);
    height: clamp(15rem, 8.972rem + 28.0374vw, 30rem);

    gap: 0.3125rem;

    &.grid-rows {
        reading-flow: grid-rows;
    }
    &.grid-columns {
        reading-flow: grid-columns;
    }

    &.grid-0 {
        grid-template-areas:
            "number1 number1 number2 number3"
            "number1 number1 number4 number5"
            "number1 number1 number6 number7"
            "number1 number1 number8 number9"
            "number1 number1 number8 number9"
            "number1 number1 number8 number9";
    }

    &.grid-1 {
        grid-template-areas:
            "number2 number1 number1 number4"
            "number2 number1 number1 number5"
            "number2 number1 number1 number6"
            "number3 number1 number1 number7"
            "number3 number1 number1 number8"
            "number3 number1 number1 number9";
    }
    &.grid-2 {
        grid-template-areas:
            "number2 number2 number1 number4"
            "number2 number2 number1 number5"
            "number2 number2 number1 number6"
            "number2 number2 number3 number7"
            "number2 number2 number3 number8"
            "number2 number2 number3 number9";
    }

    &.grid-3 {
        grid-template-areas:
            "number2 number3 number4 number5"
            "number6 number1 number1 number7"
            "number6 number1 number1 number7"
            "number8 number1 number1 number9"
            "number8 number1 number1 number9"
            "number8 number1 number1 number9";
    }

    &.grid-4 {
        grid-template-areas:
            "number3 number1 number1 number4"
            "number3 number1 number1 number5"
            "number3 number2 number2 number6"
            "number3 number2 number2 number7"
            "number3 number2 number2 number8"
            "number3 number2 number2 number9";
    }

    &.grid-5 {
        grid-template-areas:
            "number2 number3 number4 number1"
            "number5 number6 number7 number1"
            "number8 number9 number9 number1"
            "number8 number9 number9 number1"
            "number8 number9 number9 number1"
            "number8 number9 number9 number1";
    }

    &.grid-6 {
        grid-template-areas:
            "number2 number3 number4 number5"
            "number6 number7 number8 number9"
            "number6 number1 number1 number1"
            "number6 number1 number1 number1"
            "number6 number1 number1 number1"
            "number6 number1 number1 number1";
    }

    &.grid-7 {
        grid-template-areas:
            "number1 number1 number2 number4"
            "number1 number1 number2 number4"
            "number3 number3 number2 number4"
            "number5 number6 number7 number8"
            "number9 number9 number9 number9"
            "number9 number9 number9 number9";
    }

    &.grid-8 {
        grid-template-areas:
            "number2 number1 number1 number4"
            "number2 number1 number1 number5"
            "number2 number1 number1 number6"
            "number3 number1 number1 number7"
            "number3 number1 number1 number8"
            "number9 number9 number9 number9";
    }

    & a {
        display: grid;
        place-items: center;
        padding: 0.3125rem;
        text-decoration: none;
        background-color: var(--el-bg);
        background-color: var(--link-blue);
        color: var(--body-bg);
        pointer-events: none;
        font-size: clamp(1.5rem, 1.2991rem + 0.9346vw, 2rem);
        font-weight: var(--bold);

        &:focus-visible {
            @media (prefers-reduced-motion: no-preference) {
                transition: background-color 250ms linear;
            }
            background-color: var(--highlight);
            outline: 0;
            color: black;
        }

        & span {
            text-box: trim-both cap alphabetic;
        }
    }
}

.number-1 {
    grid-area: number1;
}

.number-2 {
    grid-area: number2;
}

.number-3 {
    grid-area: number3;
}

.number-4 {
    grid-area: number4;
}

.number-5 {
    grid-area: number5;
}

.number-6 {
    grid-area: number6;
}

.number-7 {
    grid-area: number7;
}

.number-8 {
    grid-area: number8;
}

.number-9 {
    grid-area: number9;
}

.page-footer {
    padding-block: 2rem;
    text-align: center;
}

/* Theme */
.theme-toggler {
    position: absolute;
    top: 0;
    right: 0;
    display: flex;
    align-items: center;
    gap: 0.625rem;
    padding: 0.3125rem 0.625rem;
    margin-block-start: 0;
    border: 0;

    & button {
        font-size: clamp(0.875rem, 0.8248rem + 0.2336vw, 1rem);
        font-family: inherit;
        background-color: var(--link-blue);

        width: 1.5625rem;
        height: 0.8125rem;
        border: 0;
        border-radius: 1.25rem;
        display: flex;
        justify-content: flex-start;
        align-items: center;
        padding: 0.125rem;
        cursor: pointer;

        & span {
            height: 0.8125rem;
            width: 0.8125rem;
            background-color: white;
            border-radius: 50%;
        }
    }

    & p {
        font-size: 0.875rem;
        font-weight: 600;
        color: var(--body-fg);
        &.light {
            opacity: 1;
        }

        &.dark {
            opacity: 0.5;
        }
    }
}

.darkmode {
    & .theme-toggler button {
        justify-content: flex-end;
    }

    & p {
        &.light {
            opacity: 0.5;
        }

        &.dark {
            opacity: 1;
        }
    }
}

/* Loader */
.loader {
    position: fixed;
    z-index: 500;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--body-bg);
    color: var(--body-fg);
}

.loader-hidden {
    opacity: 0;
    visibility: hidden;
}

.loader::after {
    content: "Loading...";
    font-size: 3.125rem;
}

@media (prefers-reduced-motion: no-preference) {
    .loader {
        transition:
            opacity 0.75s,
            visibility 0.75s;
    }

    .loader::after {
        content: "";
        font-size: 0rem;
        width: 6.25rem;
        height: 6.25rem;
        border: 1.25rem solid var(--body-fg);
        border-top-color: var(--loader);
        border-radius: 50%;
        animation: loading 0.75s ease infinite;
    }
    @keyframes loading {
        from {
            transform: rotate(0turn);
        }
        to {
            transform: rotate(1turn);
        }
    }
}

/** Skip link */
.skip-link {
    background-color: var(--body-bg);
    color: var(--body-fg);
    font-weight: 600;
    padding: 0.3125rem 0.625rem;
    margin-block-start: 0;
    margin-inline-end: 0.625rem;
}
.element-invisible {
    clip: rect(0.0625rem, 0.0625rem, 0.0625rem, 0.0625rem);
    height: 0.0625rem;
    overflow: hidden;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 200;
    &.element-focusable:active,
    &.element-focusable:focus {
        clip: auto;
        height: auto;
        overflow: visible;
    }
}

.visually-hidden {
    position: absolute;
    width: 0.0625rem;
    height: 0.0625rem;
    padding: 0;
    margin: -0.0625rem;
    overflow: hidden;
    clip-path: inset(0);
    border: 0;
}