/* =============================================================================
   CSE 110 Lab — stylesheet checklist
   Section comments group related requirements for easier grading / reading.
   ============================================================================= */

/* --- Universal selector + CSS variables (with fallback) + wider-gamut + color-mix --- */
* {
    box-sizing: border-box;
}

:root {
    /* CSS variable with fallback is demonstrated where used: var(--accent, orange) */
    --accent: rgb(46, 125, 204);
    --accent-soft: rgba(46, 125, 204, 0.12);
    --surface: hsl(210, 40%, 98%);
    --surface-muted: hsla(210, 25%, 92%, 0.95);
    --text: #1a2332;
    --text-inverse: #ffffff;
    --radius-lg: 12px;
    --font-sans: "DM Sans", system-ui, sans-serif;
    --font-serif: "Source Serif 4", Georgia, "Times New Roman", serif;
    --space-unit: 1rem;
}

/* --- Element selectors + nested selectors (native CSS nesting, 2023) --- */
html {
    scroll-behavior: smooth;
}

body {
    position: static;
    margin: 0;
    font-family: var(--font-sans, system-ui, sans-serif);
    color: var(--text, #222);
    background-color: var(--surface-muted);
    line-height: 1.55;
    min-height: 100vh;
    width: 100%;
    max-width: 56rem;
    min-width: 16rem;
    margin-left: auto;
    margin-right: auto;
    padding-top: 0.75rem;
    padding-bottom: 1.5rem;
    padding-left: 1rem;
    padding-right: 1rem;

    /* Nested selector block */
    & > header {
        margin-bottom: 1rem;
    }

    & > footer {
        margin-top: 2rem;
        text-align: center;

        & p {
            position: static;
        }
    }
}

/* --- Class selector --- */
.site-header {
    position: sticky;
    top: 0;
    z-index: 20;
    background-color: hsl(212, 42%, 96%);
    border-radius: var(--radius-lg);
    width: 100%;
    padding: 0.35rem 0.4rem 0.6rem;
    /* color-mix for header tint */
    background-color: color-mix(in srgb, hsl(212, 42%, 96%) 82%, var(--accent) 18%);

    & .purpose-heading {
        margin-bottom: 0.25rem;
    }
}

/* --- ID selector --- */
#page-root {
    position: relative;
}

/* --- Attribute selector --- */
[data-section="toc"] {
    background-color: #fff;
    border-radius: 10px;
}

[data-badge="minutes"] {
    display: inline-block;
    font-size: 0.75rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    padding: 0.2rem 0.45rem;
    border-radius: 999px;
    background-color: var(--accent-soft);
    color: var(--accent, orange);
}

.header-intro {
    padding-right: 2vw;
}

.date-highlight {
    color: rgba(30, 58, 95, 0.95);
}

.status-present {
    color: rgb(200, 48, 48);
    font-weight: 600;
}

.text-accent {
    color: hsl(215, 85%, 38%);
}

.notes-indent {
    display: block;
    margin-left: 1.25rem;
}

.style-sampler {
    max-width: min(12cm, 100%);
}

/* --- Combining selectors (element.class) --- */
section.attendance {
    border-top: 3px solid rgba(46, 125, 204, 0.25);
}

h1.title-main {
    font-family: var(--font-serif, Georgia, serif);
    font-weight: 600;
    margin: 0;
    /* hex short form */
    color: #1e3a5f;
    text-align: left;
}

/* --- Selector list (element, element) --- */
h2,
h3 {
    font-family: var(--font-serif, Georgia, serif);
    color: hsl(215, 45%, 22%);
    text-decoration: underline;
    text-decoration-color: rgba(46, 125, 204, 0.35);
    text-underline-offset: 0.18em;
}

/* --- Text: color, text-decoration, text-align --- */
p.lede {
    color: rgb(33, 48, 66);
    text-align: justify;
    text-decoration: none;
}

/* Named color example */
.mark-warn {
    color: orange;
}

/* display: none (checklist: removes element from layout) */
.checklist-hidden {
    display: none;
}

/* visually skip link until keyboard focus */
.skip-link {
    position: absolute;
    left: -9999px;
    top: auto;
    width: 1px;
    height: 1px;
    overflow: hidden;
}

.skip-link:focus {
    position: static;
    width: auto;
    height: auto;
    padding: 0.5rem 0.75rem;
    margin-bottom: 0.5rem;
    display: inline-block;
    background: navy;
    color: white;
    z-index: 100;
}

/* --- Descendant combinator (element element) --- */
main section {
    background-color: #ffffff;
    margin-bottom: 1rem;
}

/* --- Child combinator (main > section) --- */
main > section {
    border-radius: 10px;
    padding: 1rem 1rem 1.1rem;
}

/* --- Adjacent sibling combinator (h2 + p) --- */
h2 + p {
    margin-top: 0.35rem;
    color: hsla(215, 30%, 30%, 0.95);
}

/* --- General sibling combinator (h2 ~ p) --- */
h2 ~ p {
    max-width: 42rem;
}

/* --- :has() relational selector --- */
section:has(figure) {
    border-left: 4px solid var(--accent, orange);
    padding-left: 0.85rem;
}

section:has(video) {
    background-color: rgba(46, 125, 204, 0.06);
}

/* --- Pseudo-class selectors (examples include a:hover, button:active) --- */
a:hover {
    color: rgb(38, 114, 217);
    color: color(display-p3 0.15 0.45 0.85);
    text-decoration-thickness: 2px;
}

button:active {
    transform: translateY(1px);
}

main > section p:hover {
    transition: color 0.15s ease;
    color: hsl(215, 35%, 28%);
}

/* --- Flexbox: >2 children, 3+ flex properties --- */
.header-flex {
    display: flex;
    flex-direction: row;
    flex-wrap: nowrap;
    justify-content: space-between;
    align-items: flex-start;
    gap: 1rem;
    padding: 0.75rem 1rem;
}

.header-flex > * {
    flex: 1 1 0;
}

.header-flex > .header-intro {
    flex: 2.2 1 22rem;
}

.header-flex > .box-margin-long {
    flex: 1.15 1 15rem;
    margin: 0;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-self: flex-start;
}

.header-flex > .stats-grid {
    flex: 1.1 1 16rem;
    margin-top: 0;
    align-self: flex-start;
}

/* --- Grid: >2 children, 3+ grid properties --- */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 0.65rem;
    justify-items: stretch;
    align-items: stretch;
    margin-top: 0.75rem;
}

.stat-card {
    background: #f7f9fc;
    border-radius: 8px;
    padding: 0.55rem 0.6rem;
    text-align: center;
    font-size: 0.9rem;
    min-height: auto;
    width: 100%;
}

/* --- Box model: margin longhand --- */
.box-margin-long {
    margin-top: 0.5rem;
    margin-right: 0.25rem;
    margin-bottom: 0.75rem;
    margin-left: 0.25rem;
}

/* --- Box model: margin shorthand --- */
.box-margin-short {
    margin: 0.4rem 0.6rem 0.6rem 0.4rem;
}

/* --- margin: auto --- */
.centered-block {
    display: block;
    width: fit-content;
    margin: auto;
}

/* --- Padding longhand --- */
.box-pad-long {
    padding-top: 0.6rem;
    padding-right: 0.75rem;
    padding-bottom: 0.6rem;
    padding-left: 0.75rem;
}

/* --- Padding shorthand --- */
.box-pad-short {
    padding: 0.5rem 0.75rem 0.65rem 0.75rem;
}

/* --- Borders: longhand properties --- */
.box-border-long {
    border-style: solid;
    border-color: rgb(46, 125, 204);
    border-width: 1px;
    border-radius: 8px;
}

/* --- Borders shorthand --- */
.box-border-short {
    border: 2px dashed hsl(28, 85%, 42%);
    border-radius: 6px;
}

/* --- Sizing: height, width, max-width, min-width --- */
.media-row {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    gap: 1rem;
    align-items: flex-start;
}

.media-row img {
    width: 200px;
    max-width: 100%;
    min-width: 120px;
    height: auto;
    border-radius: 8px;
}

.media-aside {
    flex: 1 1 14rem;
    margin: 0;
    font-size: 0.9rem;
    color: hsl(215, 20%, 35%);
}

video {
    max-width: 100%;
    height: auto;
}

/* --- Display experiments: block, inline-block, inline --- */
.tag-inline {
    display: inline;
    font-weight: 600;
}

.pill-inline-block {
    display: inline-block;
    padding: 0.15rem 0.45rem;
    border-radius: 999px;
    background: lavender;
}

/* --- Position: relative + fixed (two of the required set) --- */
.corner-note {
    position: fixed;
    right: 0.75rem;
    bottom: 0.75rem;
    width: 9.5rem;
    padding: 0.45rem 0.55rem;
    font-size: 0.78rem;
    background: rgba(255, 255, 255, 0.92);
    border: 1px solid #ccd6e4;
    border-radius: 8px;
    box-shadow: 0 4px 14px rgba(0, 0, 0, 0.08);
    z-index: 30;
}

main {
    position: relative;
}

/* --- Form --- */
form[action="/submit"] {
    display: block;
    background: #fff;
    border-radius: 12px;
    padding: 1rem;
    margin-top: 1rem;
}

fieldset {
    border: 1px solid #cfd8e6;
    border-radius: 10px;
}

button[type="submit"] {
    display: inline-block;
    padding: 0.45rem 0.9rem;
    border-radius: 8px;
    border: 1px solid var(--accent, orange);
    background: var(--accent, orange);
    color: var(--text-inverse);
    font-family: var(--font-sans);
    cursor: pointer;
}

/* --- Units showcase (3 relative + 3 absolute) ---
   Relative: rem, %, em  |  Absolute: px, pt, cm --- */
.unit-demo {
    font-size: 0.95rem;
    width: 92%;
    max-width: 100%;
    margin: 0.5rem 0;
    padding: 9pt 12pt;
    border-left: 3px solid #2e7dcc;
    padding-left: 1.2em;
    min-height: 3rem;
}

/* --- hr --- */
hr {
    border: none;
    border-top: 1px solid #d5deea;
    margin: 1rem 0;
}

/* --- details / nav --- */
details {
    padding: 0.5rem 0.75rem;
}

nav ul {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: flex-start;
    align-items: center;
    gap: 0.35rem 0.75rem;
    list-style: none;
    padding: 0;
    margin: 0.25rem 0 0;
}

nav a {
    text-decoration: none;
    color: var(--accent, orange);
}

/* --- Responsiveness: width-based media queries --- */
@media (max-width: 36rem) {
    body {
        padding-left: 0.65rem;
        padding-right: 0.65rem;
    }

    .stats-grid {
        grid-template-columns: 1fr;
    }

    .header-flex {
        flex-direction: column;
        align-items: flex-start;
        flex-wrap: wrap;
    }

    .header-flex > .header-intro,
    .header-flex > .box-margin-long,
    .header-flex > .stats-grid {
        width: 100%;
        flex: 1 1 auto;
    }

    .corner-note {
        position: static;
        width: 100%;
        margin-top: 0.75rem;
    }
}

@media (min-width: 36.01rem) and (max-width: 60rem) {
    body {
        max-width: 42rem;
    }

    .stats-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (min-width: 60.01rem) {
    body {
        max-width: 56rem;
    }
}