index.css

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

:root {
    overflow-y: scroll;
    --brand: #031d55;
    --border-radius: 0.3125rem;
    --button-border-radius: 100vw;
    --shadow: 0.1875rem 0.1875rem 0.3125rem 0rem rgba(0, 0, 0, 0.33);
    --bg: white;
    --fg: black;
    --bg-main: #f3f5f2;
    --bg-form: #d4dfce;
    --main-link: blue;
    --filter-color: rgb(0, 0, 0, 0.5);
    --button-bg: #0075ff;
}

.darkmode {
    --bg: black;
    --fg: white;
    --main-link: aqua;
    --bg-main: #302d4f;
    --bg-form: #3d3969;
    --filter-color: rgb(0, 0, 0, 1);
}

:focus-visible {
    outline: 0.125rem solid orange;
    outline-offset: 0.1875rem;
}
body {
    font-family: system-ui, sans-serif;
    line-height: 1.5;
    font-size: clamp(1rem, 0.8995rem + 0.4673vw, 1.25rem);

    min-height: 100vh;
    min-height: 100dvh;
    display: grid;
    grid-template-rows: auto 1fr auto;
}

.h1 {
    font-size: clamp(1.25rem, 0.7477rem + 2.3364vw, 2.5rem);
}
h1 {
    font-size: clamp(1.25rem, 0.8732rem + 1.7523vw, 2.1875rem);
}

h1,
.h1 {
    font-weight: normal;
    text-wrap: balance;
}

h2 {
    font-size: clamp(1.25rem, 0.9988rem + 1.1682vw, 1.875rem);
    font-weight: normal;
    line-height: 1;
}
h1,
h2 {
    text-align: center;
}

h1 + p {
    width: fit-content;
    margin-inline: auto;
    text-wrap: auto;
}

img {
    max-width: 100%;
    height: auto;
    display: block;

    filter: drop-shadow(0.25rem 0.5625rem 0.25rem var(--filter-color));
}

p {
    text-wrap: balance;

    &:empty {
        display: none;
    }
}

a {
    text-decoration: none;
    text-underline-offset: 0.375rem;
}

svg {
    height: clamp(2rem, 1.5981rem + 1.8692vw, 3rem);
    width: clamp(2rem, 1.5981rem + 1.8692vw, 3rem);
    display: block;
    fill: white;
}

button {
    all: unset;
    cursor: pointer;
}

.main .button,
.main button {
    border-radius: var(--button-border-radius);
    border: 0.125rem solid transparent;

    @media (hover: hover) {
        &:hover {
            border: 0.125rem solid var(--fg);
        }
    }
}

select {
    font-family: inherit;
    font-size: inherit;
}

.uppercase {
    text-transform: uppercase;
}

.container {
    /* Locally-scoped CSS variables */
    --_content-max-width: 50rem;
    --_content-space-outside: 1.25rem;

    width: min(var(--_content-max-width), 100% - var(--_content-space-outside) * 2);
    margin-inline: auto;
}

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

.header,
.footer {
    background-color: var(--brand);
    color: white;
    padding-inline: 1.25rem;

    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1.25rem;
    padding: 2.5rem 1.25rem;

    & a {
        color: white;
    }
}

.footer {
    & a {
        @media (hover: hover) {
            &:hover {
                text-decoration: underline;
            }
        }

        &::after {
            content: " \27F6";
        }
    }
}

.title {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.625rem;
}

.main-navigation {
    & ul {
        list-style-type: "";
        display: flex;
        gap: 1.25rem;
        padding-inline-start: 0;
        font-size: clamp(0.9375rem, 0.8621rem + 0.3505vw, 1.125rem);
        font-weight: 600;
    }

    & a {
        border-radius: var(--border-radius);
        padding: 0.3125rem 0.5rem;
        &[aria-current="page"] {
            background-color: white;
            color: black;
        }
    }
}

&[aria-current="page"] {
    background-color: white;
    color: black;
}

.main {
    padding-block: 2.5rem;
    display: flex;
    flex-direction: column;
    gap: 2.8125rem;
    background-color: var(--bg-main);
    color: var(--fg);

    & a {
        color: var(--main-link);
    }

    & ul {
        padding-inline-start: 1.125rem;
    }

    & p,
    & li,
    & dt {
        font-family: Georgia, "Times New Roman", Times, serif;
        text-wrap: pretty;
    }

    & button,
    & .button {
        padding: 0.5rem 1rem;
        background-color: var(--button-bg);
        color: white;
        font-weight: 600;

        @media (hover: hover) {
            &:hover {
                opacity: 0.7;
            }
        }
    }
}

.row {
    display: flex;
    flex-wrap: wrap;
    gap: 2.5rem;
    justify-content: space-around;
    width: fit-content;
    margin-inline: auto;

    & > section {
        margin-inline: auto;
    }
}

/* Shared */
form,
dl {
    min-width: 11.8125rem;
}

/* Order form */
form {
    padding: 1.25rem 0.9375rem;
    background-color: var(--bg-form);
    border: 0.125rem solid var(--filter-color);
    border-radius: var(--border-radius);
    width: fit-content;
    margin-inline: auto;
    display: flex;
    flex-direction: column;
    gap: 0.625rem;
    justify-content: space-between;

    & fieldset {
        border: 0.0625rem solid var(--filter-color);
        border-radius: var(--border-radius);
    }

    & div {
        display: flex;
        gap: 0.625rem;
    }

    & label {
        flex-grow: 1;
        text-align: right;
    }

    & input {
        font-size: inherit;
        border: 0.0625rem solid var(--filter-color);
        border-radius: var(--border-radius);
    }

    & button {
        margin-inline: auto;
    }

    .quantity {
        max-width: 5ch;
    }

    .colour-radios {
        display: flex;
        flex-direction: column;
        gap: 0;

        & label {
            display: flex;
            gap: 0.5rem;
        }
    }
}

/** Checkout */

.checkout {
    &.row {
        align-items: flex-start;
        margin-block-end: 3rem;
    }

    dl {
        display: grid;
        grid-gap: 0.25rem 1rem;
    }
    dt {
        font-weight: 600;
    }
    dd {
        margin: 0;
        grid-column-start: 2;
    }
}

.checkout-buttons {
    display: flex;
    gap: 2rem;
    margin-inline: auto;

    & button:disabled {
        cursor: not-allowed;
        margin-inline-start: auto;
        background-color: #ccc;
        color: black;
        opacity: 0.6;

        @media (hover: hover) {
            &:hover {
                opacity: 0.6;
                border-color: transparent;
            }
        }
    }
}

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

    & button {
        font-size: clamp(0.875rem, 0.8248rem + 0.2336vw, 1rem);
        font-family: inherit;
        background-color: var(--button-bg);
        width: 1.5625rem;
        height: 0.8125rem;
        border-radius: 1.25rem;
        display: flex;
        justify-content: flex-start;
        align-items: center;
        padding: 0.125rem;

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

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

        &.dark {
            opacity: 0.75;
        }
    }
}

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

    & p {
        &.light {
            opacity: 0.75;
        }

        &.dark {
            opacity: 11;
        }
    }
}
/* End theme */

/** Skip link */
.skip-link {
    color: white;
    text-decoration: none;
    font-weight: 600;
    padding: 0.3125rem 0.625rem;
    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;
}