:root {
    /* Typography */
    --sans-font: -apple-system, BlinkMacSystemFont, "Avenir Next", Avenir,
        "Nimbus Sans L", Roboto, "Noto Sans", "Segoe UI",
        Arial, Helvetica, "Helvetica Neue", sans-serif;
    --mono-font: Consolas, Menlo, Monaco, "Andale Mono", "Ubuntu Mono", monospace;

    /* Layout / UI */
    --standard-border-radius: 5px;
    --border-width: 1px;

    /* Light‑mode palette */
    --bg: #fff;
    --accent-bg: #f5f7ff;
    --text: #212121;
    --text-light: #585858;
    --border: #898ea4;
    --accent: #0d47a1;
    --accent-hover: #1266e2;
    --accent-text: var(--bg);
    --code: #d81b60;
    --preformatted: #444;
    --marked: #fd3;
    --disabled: #efefef;
}

/* Dark‑mode overrides */
@media (prefers-color-scheme: dark) {
    :root {
        color-scheme: dark;
        --bg: #212121;
        --accent-bg: #2b2b2b;
        --text: #dcdcdc;
        --text-light: #ababab;
        --accent: #ffb300;
        --accent-hover: #ffe099;
        --accent-text: var(--bg);
        --code: #f06292;
        --preformatted: #ccc;
        --disabled: #111;
    }
    img,
    video {
        opacity: .8;
    }
}

/* Global reset */
*,
:before,
:after {
    box-sizing: border-box;
}
textarea,
select,
input,
progress {
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
}
html {
    font-family: var(--sans-font);
    scroll-behavior: smooth;
}

/* Page layout – CSS Grid */
body {
    color: var(--text);
    background-color: var(--bg);
    display: grid;
    grid-template-columns: 1fr min(70rem, 90%) 1fr;
    margin: 0;
    font-size: 1.15rem;
    line-height: 1.5;
}
body > * {
    grid-column: 2;
}

/* Header & Footer */
body > header {
    background-color: var(--accent-bg);
    border-bottom: var(--border-width) solid var(--border);
    text-align: center;
    grid-column: 1 / -1;
    padding: 0 .5rem 2rem;
}
body > header > :only-child {
    margin-block-start: 2rem;
}
body > header h1 {
    max-width: 1200px;
    margin: 1rem auto;
}
body > header p {
    max-width: 40rem;
    margin: 1rem auto;
}
main {
    padding-top: 1.5rem;
}
body > footer {
    color: var(--text-light);
    text-align: center;
    border-top: var(--border-width) solid var(--border);
    margin-top: 4rem;
    padding: 2rem 1rem 1.5rem;
    font-size: .9rem;
}

/* Typography hierarchy */
h1 {
    font-size: 3rem;
}
h2 {
    margin-top: 3rem;
    font-size: 2.6rem;
}
h3 {
    margin-top: 3rem;
    font-size: 2rem;
}
h4 {
    font-size: 1.44rem;
}
h5 {
    font-size: 1.15rem;
}
h6 {
    font-size: .96rem;
}
p {
    margin: 1.5rem 0;
}
p,
h1,
h2,
h3,
h4,
h5,
h6 {
    overflow-wrap: break-word;
}
h1,
h2,
h3 {
    line-height: 1.1;
}

/* Responsive typography (≤720px) */
@media only screen and (width <= 720px) {
    h1 {
        font-size: 2.5rem;
    }
    h2 {
        font-size: 2.1rem;
    }
    h3 {
        font-size: 1.75rem;
    }
    h4 {
        font-size: 1.25rem;
    }
}

/* Links */
a,
a:visited {
    color: var(--accent);
}
a:hover {
    text-decoration: none;
}

/* Buttons & form controls */
button,
.button,
a.button,
input[type=submit],
input[type=reset],
input[type=button] {
    border: var(--border-width) solid var(--accent);
    background-color: var(--accent);
    color: var(--accent-text);
    padding: .5rem .9rem;
    line-height: normal;
    text-decoration: none;
}
.button[aria-disabled=true],
input:disabled,
textarea:disabled,
select:disabled,
button[disabled] {
    cursor: not-allowed;
    background-color: var(--disabled);
    border-color: var(--disabled);
    color: var(--text-light);
}
input[type=range] {
    padding: 0;
}
abbr[title] {
    cursor: help;
    text-decoration-line: underline;
    text-decoration-style: dotted;
}
button:enabled:hover,
.button:not([aria-disabled=true]):hover,
input[type=submit]:enabled:hover,
input[type=reset]:enabled:hover,
input[type=button]:enabled:hover {
    background-color: var(--accent-hover);
    border-color: var(--accent-hover);
    cursor: pointer;
}
.button:focus-visible,
button:focus-visible:where(:enabled),
input:enabled:focus-visible:where([type=submit], [type=reset], [type=button]) {
    outline: 2px solid var(--accent);
    outline-offset: 1px;
}

/* Header navigation */
.menu .menu{
    display: flex;
    list-style-type: none;
    margin: 0;
    padding: 0;
}

.item{
    margin: 5px 20px;
}
header nav {
    padding: 1rem 0 0;
    font-size: 1rem;
    line-height: 2;
}
header nav ul,
header nav ol {
    display: flex;
    flex-flow: wrap;
    place-content: space-around center;
    align-items: center;
    margin: 0;
    padding: 0;
    list-style-type: none;
}
header nav ul li,
header nav ol li {
    display: inline-block;
}
header nav a,
header nav a:visited {
    border: var(--border-width) solid var(--border);
    border-radius: var(--standard-border-radius);
    color: var(--text);
    margin: 0 .5rem 1rem;
    padding: .1rem 1rem;
    text-decoration: none;
    display: inline-block;
}
header nav a:hover,
header nav a.current,
header nav a[aria-current=page],
header nav a[aria-current=true] {
    background: var(--bg);
    border-color: var(--accent);
    color: var(--accent);
    cursor: pointer;
}

/* Nav responsive (≤720px) */
@media only screen and (width <= 720px) {
    header nav a {
        border: none;
        padding: 0;
        line-height: 1;
        text-decoration: underline;
    }
    header nav a.current {
        background: 0 0;
    }
}

/* Panels, asides, details, pre, progress */
aside,
details,
pre,
progress {
    background-color: var(--accent-bg);
    border: var(--border-width) solid var(--border);
    border-radius: var(--standard-border-radius);
    margin-bottom: 1rem;
}

/* Aside specifics */
aside {
    float: right;
    width: 30%;
    margin-inline-start: 15px;
    padding: 0 15px;
    font-size: 1rem;
}
[dir=rtl] aside {
    float: left;
}
@media only screen and (width <= 720px) {
    aside {
        float: none;
        width: 100%;
        margin-inline-start: 0;
    }
}

/* Articles, fieldsets, dialogs */
article,
fieldset,
dialog {
    border: var(--border-width) solid var(--border);
    border-radius: var(--standard-border-radius);
    margin-bottom: 1rem;
    padding: 1rem;
}
article h2:first-child,
section h2:first-child,
article h3:first-child,
section h3:first-child {
    margin-top: 1rem;
}

/* Sections */
section {
    border-top: var(--border-width) solid var(--border);
    border-bottom: var(--border-width) solid var(--border);
    margin: 3rem 0;
    padding: 2rem 1rem;
}
section + section,
section:first-child {
    border-top: 0;
    padding-top: 0;
}
section + section {
    margin-top: 0;
}
section:last-child {
    border-bottom: 0;
    padding-bottom: 0;
}

/* Details & summary */
details {
    padding: .7rem 1rem;
}
summary {
    cursor: pointer;
    word-break: break-all;
    margin: -.7rem -1rem;
    padding: .7rem 1rem;
    font-weight: 700;
}
details[open] > summary + * {
    margin-top: 0;
}
details[open] > summary {
    margin-bottom: .5rem;
}
details[open] > :last-child {
    margin-bottom: 0;
}

/* Tables */
table {
    border-collapse: collapse;
    margin-left: auto;
    margin-right: auto;
}
figure > table {
    width: max-content;
    margin: 0;
}
td,
th {
    border: var(--border-width) solid var(--border);
    text-align: start;
    padding: .5rem;
}
th {
    background-color: var(--accent-bg);
    font-weight: 700;
}
tr:nth-child(2n) {
    background-color: var(--accent-bg);
}
table caption {
    margin-bottom: .5rem;
    font-weight: 700;
}

/* Form controls (continued) */
textarea,
select,
input,
button,
.button {
    font-size: inherit;
    border-radius: var(--standard-border-radius);
    box-shadow: none;
    max-width: 100%;
    margin-bottom: .5rem;
    padding: .5em;
    font-family: inherit;
    display: inline-block;
}
textarea,
select,
input {
    color: var(--text);
    background-color: var(--bg);
    border: var(--border-width) solid var(--border);
}
label {
    display: block;
}
textarea:not([cols]) {
    width: 100%;
}
select:not([multiple]) {
    background-image:
        linear-gradient(45deg, transparent 49%, var(--text) 51%),
        linear-gradient(135deg, var(--text) 51%, transparent 49%);
    background-position: calc(100% - 15px), calc(100% - 10px);
    background-repeat: no-repeat;
    background-size: 5px 5px, 5px 5px;
    padding-inline-end: 25px;
}
[dir=rtl] select:not([multiple]) {
    background-position: 10px, 15px;
}
input[type=checkbox],
input[type=radio] {
    vertical-align: middle;
    width: min-content;
    position: relative;
}
input[type=checkbox] + label,
input[type=radio] + label {
    display: inline-block;
}
input[type=radio] {
    border-radius: 100%;
}
input[type=checkbox]:checked,
input[type=radio]:checked {
    background-color: var(--accent);
}
input[type=checkbox]:checked:after {
    content: " ";
    border-right: solid var(--bg) .08em;
    border-bottom: solid var(--bg) .08em;
    background-color: #0000;
    border-radius: 0;
    width: .2em;
    height: .4em;
    font-size: 1.8em;
    position: absolute;
    top: .04em;
    left: .18em;
    transform: rotate(45deg);
}
input[type=radio]:checked:after {
    content: " ";
    background-color: var(--bg);
    border-radius: 100%;
    width: .3em;
    height: .3em;
    font-size: 1.8em;
    position: absolute;
    top: .125em;
    left: .125em;
}

/* Responsive inputs (≤720px) */
@media only screen and (width <= 720px) {
    textarea,
    select,
    input {
        width: 100%;
    }
}

/* Colour pickers & file inputs */
input[type=color] {
    height: 2.5rem;
    padding: .2rem;
}
input[type=file] {
    border: 0;
}

/* Horizontal rule */
hr {
    height: var(--border-width);
    background: var(--border);
    border: none;
    margin: 1rem auto;
}

/* Mark (highlight) */
mark {
    border-radius: var(--standard-border-radius);
    background-color: var(--marked);
    color: #000;
    padding: 2px 5px;
}
mark a {
    color: #0d47a1;
}

/* Images & video */
img,
video {
    border-radius: var(--standard-border-radius);
    max-width: 100%;
    height: auto;
}

/* Figure & caption */
figure {
    margin: 0;
    display: block;
    overflow-x: auto;
}
figure > img,
figure > picture > img {
    margin-inline: auto;
    display: block;
}
figcaption {
    text-align: center;
    color: var(--text-light);
    margin-block: 1rem;
    font-size: .9rem;
    position: sticky;
    left: 0;
}

/* Blockquote */
blockquote {
    border-inline-start: .35rem solid var(--accent);
    color: var(--text-light);
    margin-block: 2rem;
    margin-inline: 2rem 0;
    padding: .4rem .8rem;
    font-style: italic;
}
cite {
    color: var(--text-light);
    font-size: .9rem;
    font-style: normal;
}

/* Definition term */
dt {
    color: var(--text-light);
}

/* Code & pre */
code,
pre,
pre span,
kbd,
samp {
    font-family: var(--mono-font);
    color: var(--code);
}
kbd {
    color: var(--preformatted);
    border: var(--border-width) solid var(--preformatted);
    border-bottom: 3px solid var(--preformatted);
    border-radius: var(--standard-border-radius);
    padding: .1rem .4rem;
}
pre {
    max-width: 100%;
    color: var(--preformatted);
    padding: 1rem 1.4rem;
    overflow: auto;
}
pre code {
    color: var(--preformatted);
    background: 0 0;
    margin: 0;
    padding: 0;
}

/* Progress bar */
progress {
    width: 100%;
}
progress:indeterminate {
    background-color: var(--accent-bg);
}
progress::-webkit-progress-bar {
    border-radius: var(--standard-border-radius);
    background-color: var(--accent-bg);
}
progress::-webkit-progress-value {
    border-radius: var(--standard-border-radius);
    background-color: var(--accent);
}
progress::-moz-progress-bar {
    border-radius: var(--standard-border-radius);
    background-color: var(--accent);
    transition-property: width;
    transition-duration: .3s;
}
progress:indeterminate::-moz-progress-bar {
    background-color: var(--accent-bg);
}

/* Dialog */
dialog {
    background-color: var(--bg);
    max-width: 40rem;
    margin: auto;
}
dialog::backdrop {
    background-color: var(--bg);
    opacity: .8;
}
@media only screen and (width <= 720px) {
    dialog {
        max-width: calc(100vw - 2rem);
    }
}

/* Superscript & subscript */
sup,
sub {
    vertical-align: baseline;
    position: relative;
}
sup {
    top: -.4em;
}
sub {
    top: .3em;
}

/* Notice box */
.notice {
    background: var(--accent-bg);
    border: var(--border-width) solid var(--border);
    border-radius: var(--standard-border-radius);
    margin: 2rem 0;
    padding: 1.5rem;
}

/* Print styles */
@media print {
    @page {
        margin: 1cm;
    }
    body {
        display: block;
    }
    body > header {
        background-color: unset;
    }
    body > header nav,
    body > footer {
        display: none;
    }
    article {
        border: none;
        padding: 0;
    }
    a[href^="http"]:after {
        content: " <" attr(href) ">";
    }
    abbr[title]:after {
        content: " (" attr(title) ")";
    }
    a {
        text-decoration: none;
    }
    p {
        widows: 3;
        orphans: 3;
    }
    hr {
        border-top: var(--border-width) solid var(--border);
    }
    mark {
        border: var(--border-width) solid var(--border);
    }
    pre,
    table,
    figure,
    img,
    svg {
        break-inside: avoid;
    }
    pre code {
        white-space: pre-wrap;
    }
}

.menu{
    display: flex;
    list-style-type: none;
    margin: 0;
    padding: 0;
    background-color: var(--bg);
}

.item{
    margin: 5px 20px;
}