/* ==========================================================
   CARS Course Website — Style
   DESIGN.md § 14: CSS variables for everything, no magic values.
   ========================================================== */

/* ----------------------------------------------------------
   Variables
   All colors, fonts, sizes, and spacing are defined here.
   To change the palette or typography, edit only this section.
   ---------------------------------------------------------- */

:root {
  /* Colors — neutral warm palette */
  --color-text:         #2d2a26;
  --color-bg:           #faf9f7;
  --color-accent:       #b45309;
  --color-accent-hover: #92400e;
  --color-muted:        #6b6560;
  --color-border:       #e5e2de;
  --color-code-bg:      #f3f1ee;
  --color-heading:      #78350f;
  --color-focus:        #b45309;

  /* Typography */
  --font-body: "IBM Plex Sans", -apple-system, BlinkMacSystemFont,
               "Segoe UI", Roboto, sans-serif;
  --font-mono: "IBM Plex Mono", "SFMono-Regular", Consolas,
               "Liberation Mono", Menlo, monospace;
  --font-size-base:  1.125rem;
  --font-size-small: 0.9375rem;
  --font-size-h1:    2.25rem;
  --font-size-h2:    1.625rem;
  --font-size-h3:    1.3125rem;
  --line-height:     1.6;

  /* Layout */
  --max-width:       52rem;
  --spacing-xs:      0.25rem;
  --spacing-sm:      0.5rem;
  --spacing-md:      1rem;
  --spacing-lg:      2rem;
  --spacing-xl:      3rem;
}


/* ----------------------------------------------------------
   Font faces — vendored IBM Plex (DESIGN.md § 14)
   ---------------------------------------------------------- */

@font-face {
  font-family: "IBM Plex Sans";
  src: url("../fonts/IBMPlexSans-Regular.woff2") format("woff2");
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: "IBM Plex Sans";
  src: url("../fonts/IBMPlexSans-Bold.woff2") format("woff2");
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: "IBM Plex Sans";
  src: url("../fonts/IBMPlexSans-Italic.woff2") format("woff2");
  font-weight: 400;
  font-style: italic;
  font-display: swap;
}

@font-face {
  font-family: "IBM Plex Mono";
  src: url("../fonts/IBMPlexMono-Regular.woff2") format("woff2");
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: "IBM Plex Mono";
  src: url("../fonts/IBMPlexMono-Bold.woff2") format("woff2");
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}


/* ----------------------------------------------------------
   Base — reset and typography
   ---------------------------------------------------------- */

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

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
}

h1, h2, h3, h4, h5, h6 {
  line-height: 1.3;
  margin-top: var(--spacing-lg);
  margin-bottom: var(--spacing-md);
}

h1 { font-size: var(--font-size-h1); }
h2 { font-size: var(--font-size-h2); color: var(--color-heading); }
h3 { font-size: var(--font-size-h3); color: var(--color-heading); }

p, ul, ol, table, blockquote, pre {
  margin-top: 0;
  margin-bottom: var(--spacing-md);
}


/* ----------------------------------------------------------
   Skip navigation — accessibility (WCAG 2.4.1)
   ---------------------------------------------------------- */

.skip-nav {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--color-text);
  color: var(--color-bg);
  font-size: var(--font-size-small);
  text-decoration: none;
}

.skip-nav:focus {
  left: 0;
}


/* ----------------------------------------------------------
   Focus indicators — accessibility (WCAG 2.4.7)
   ---------------------------------------------------------- */

:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 2px;
}


/* ----------------------------------------------------------
   Links
   ---------------------------------------------------------- */

a {
  color: var(--color-accent);
  text-decoration: underline;
}

a:hover {
  color: var(--color-accent-hover);
}

a:visited {
  color: var(--color-accent-hover);
}


/* ----------------------------------------------------------
   Layout
   ---------------------------------------------------------- */

header, main, footer {
  max-width: var(--max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--spacing-md);
  padding-right: var(--spacing-md);
}

header {
  padding-top: var(--spacing-md);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--color-border);
}

main {
  padding-top: var(--spacing-md);
  padding-bottom: var(--spacing-xl);
}

main > :first-child {
  margin-top: var(--spacing-sm);
}

footer {
  padding-top: var(--spacing-md);
  padding-bottom: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
  color: var(--color-muted);
  font-size: var(--font-size-small);
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}

footer a {
  color: var(--color-muted);
}

footer a:hover {
  color: var(--color-accent);
}


/* ----------------------------------------------------------
   Navigation
   ---------------------------------------------------------- */

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs) var(--spacing-lg);
}

.nav-primary {
  display: flex;
  align-items: baseline;
  gap: var(--spacing-md);
}

.nav-brand {
  font-size: var(--font-size-h3);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: 0.05em;
}

.nav-brand:hover {
  color: var(--color-accent);
}

.nav-primary ul {
  gap: var(--spacing-xs) var(--spacing-md);
}

.nav-primary a:not(.nav-brand) {
  text-decoration: none;
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--color-text);
}

.nav-primary a:not(.nav-brand):hover {
  color: var(--color-accent);
  text-decoration: underline;
}

.nav-primary a.nav-active {
  color: var(--color-accent);
}

.nav-secondary {
  margin-top: var(--spacing-xs);
}

.nav-secondary a {
  text-decoration: none;
  font-size: var(--font-size-small);
  color: var(--color-muted);
}

.nav-secondary a:hover {
  color: var(--color-accent);
  text-decoration: underline;
}

.nav-secondary a.nav-active {
  color: var(--color-text);
  font-weight: 700;
}


/* ----------------------------------------------------------
   Code
   ---------------------------------------------------------- */

code, pre {
  font-family: var(--font-mono);
  font-size: var(--font-size-small);
}

code {
  background: var(--color-code-bg);
  padding: 0.1em 0.3em;
  border-radius: 3px;
}

pre {
  background: var(--color-code-bg);
  padding: var(--spacing-md);
  overflow-x: auto;
  border-radius: 4px;
}

pre code {
  background: none;
  padding: 0;
}


/* ----------------------------------------------------------
   Tables
   ---------------------------------------------------------- */

table {
  border-collapse: collapse;
  width: 100%;
}

th, td {
  text-align: left;
  padding: var(--spacing-sm) var(--spacing-md);
  border-bottom: 1px solid var(--color-border);
}

th {
  font-weight: 700;
  border-bottom-width: 2px;
}


/* ----------------------------------------------------------
   Blockquotes
   ---------------------------------------------------------- */

blockquote {
  margin-left: 0;
  padding-left: var(--spacing-md);
  border-left: 3px solid var(--color-border);
  color: var(--color-muted);
  font-style: italic;
}


/* ----------------------------------------------------------
   Tags (library page)
   ---------------------------------------------------------- */

.tag {
  display: inline-block;
  padding: 0.15em 0.5em;
  margin: 0.1em 0.2em;
  font-size: var(--font-size-small);
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  color: var(--color-muted);
}

.tags {
  margin-top: var(--spacing-sm);
}


/* ----------------------------------------------------------
   Staff cards (home page)
   ---------------------------------------------------------- */

.staff {
  margin: var(--spacing-lg) 0;
}

.staff-card {
  margin-bottom: var(--spacing-lg);
  padding-left: var(--spacing-md);
  border-left: 3px solid var(--color-border);
}

.staff-card h3 {
  margin-top: 0;
  margin-bottom: var(--spacing-xs);
}

.staff-card p {
  margin-bottom: var(--spacing-xs);
}


/* ----------------------------------------------------------
   Deliverable cards (schedule article blocks)
   ---------------------------------------------------------- */

.deliverable-card {
  padding: var(--spacing-md);
  background: var(--color-code-bg);
  border-radius: 4px;
  margin: var(--spacing-md) 0;
}

.deliverable-card h3 {
  margin-top: 0;
}


/* ----------------------------------------------------------
   Schedule article blocks
   ---------------------------------------------------------- */

article[id^="week-"] {
  padding: var(--spacing-lg) 0;
  border-bottom: 1px solid var(--color-border);
}

.week-dates {
  color: var(--color-muted);
  font-size: var(--font-size-small);
  margin-top: calc(-1 * var(--spacing-sm));
}


/* ----------------------------------------------------------
   Responsive — mobile first
   ---------------------------------------------------------- */

@media (max-width: 40rem) {
  :root {
    --font-size-h1: 1.5rem;
    --font-size-h2: 1.25rem;
    --font-size-h3: 1.1rem;
  }

  nav ul {
    flex-direction: column;
    gap: var(--spacing-xs);
  }
}