/* =============================================================================
   style.css — Global styles for Nicholas Callahan's portfolio site.

   Section order (top to bottom):
     1.  Design tokens (:root custom properties)
     2.  Minimal reset
     3.  Base typography
     4.  Layout helpers (.container, .section, .section-header)
     5.  Components (.btn, .tag, .card, .nav, .icon-link)
     6.  Section styles (hero, about, skills, projects, experience, honors,
         contact, footer)
     7.  Responsive breakpoints (mobile-first; one breakpoint at 720px)
   ============================================================================= */


/* 1. Design tokens ----------------------------------------------------------- */
:root {
  /* Color palette — light warm neutral with orange accents. */
  --bg: #FAFAF7;          /* page background */
  --surface: #FFFFFF;     /* raised surfaces: cards, nav */
  --text: #1F2937;        /* primary text */
  --muted: #6B7280;       /* secondary text, captions */
  --border: #E5E7EB;      /* hairline dividers */
  --accent: #E85D04;      /* primary accent (links, buttons) */
  --accent-hover: #C44A03;/* darker accent for hover/active states */
  --accent-soft: #FFE9D6; /* tinted background for accent chips */
  --focus: #FDB07A;       /* focus outline — meets contrast against bg */

  /* Spacing scale (4 px base, doubles up smoothly). */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-6: 24px;
  --space-8: 32px;
  --space-12: 48px;
  --space-16: 64px;
  --space-24: 96px;

  /* Typography — system font stack: zero network cost, native look on any OS. */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
               "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  /* Type scale. */
  --fs-xs: 0.8125rem;     /* 13px */
  --fs-sm: 0.9375rem;     /* 15px */
  --fs-base: 1rem;        /* 16px */
  --fs-lg: 1.125rem;      /* 18px */
  --fs-xl: 1.5rem;        /* 24px */
  --fs-2xl: 2rem;         /* 32px */
  --fs-3xl: 2.75rem;      /* 44px */

  /* Layout. */
  --container-max: 1100px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 2px rgba(17, 24, 39, 0.04);
  --shadow-md: 0 4px 14px rgba(17, 24, 39, 0.06);

  /* Nav height — also used as scroll-padding so anchor jumps clear the nav. */
  --nav-h: 64px;
}


/* 2. Minimal reset ----------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h); /* keep anchored sections below sticky nav */
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: var(--fs-base);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

a { color: var(--accent); text-decoration: none; }
a:hover, a:focus-visible { color: var(--accent-hover); text-decoration: underline; }

/* Accessible focus ring — visible on keyboard nav, hidden for mouse clicks. */
:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}


/* 3. Base typography --------------------------------------------------------- */
h1, h2, h3, h4 {
  color: var(--text);
  line-height: 1.2;
  margin: 0 0 var(--space-4);
  font-weight: 700;
}
h1 { font-size: var(--fs-3xl); letter-spacing: -0.02em; }
h2 { font-size: var(--fs-2xl); letter-spacing: -0.01em; }
h3 { font-size: var(--fs-xl); }
h4 { font-size: var(--fs-lg); }

p { margin: 0 0 var(--space-4); }

/* The orange underline beneath section titles — repeated visual motif. */
.section-header {
  margin-bottom: var(--space-8);
}
.section-header h2 {
  display: inline-block;
  padding-bottom: var(--space-2);
  border-bottom: 3px solid var(--accent);
  margin-bottom: var(--space-3);
}
/* Section-header descriptor: no fixed width, let the container handle wrap. */
.section-header p {
  color: var(--muted);
  margin: 0;
}


/* 4. Layout helpers ---------------------------------------------------------- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.section {
  padding: var(--space-16) 0;
  border-bottom: 1px solid var(--border); /* subtle separator between sections */
}
.section:last-of-type { border-bottom: none; }


/* 5. Components -------------------------------------------------------------- */

/* Buttons — primary (filled accent) and secondary (outlined). */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-md);
  font-size: var(--fs-sm);
  font-weight: 600;
  border: 2px solid transparent;
  cursor: pointer;
  transition: background-color 120ms ease, color 120ms ease,
              border-color 120ms ease, transform 120ms ease;
}
.btn--primary {
  background: var(--accent);
  color: #fff;
}
.btn--primary:hover, .btn--primary:focus-visible {
  background: var(--accent-hover);
  color: #fff;
  text-decoration: none;
}
.btn--secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border);
}
.btn--secondary:hover, .btn--secondary:focus-visible {
  border-color: var(--accent);
  color: var(--accent-hover);
  text-decoration: none;
}

/* Tag chips — used for skills, project tech stacks, coursework. */
.tag {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  margin: 0 var(--space-1) var(--space-1) 0;
  font-size: var(--fs-xs);
  background: var(--accent-soft);
  color: var(--accent-hover);
  border-radius: 999px;
  font-weight: 500;
}
.tag--neutral {
  background: var(--surface);
  color: var(--muted);
  border: 1px solid var(--border);
}

/* Card — projects, experience entries, etc. */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: box-shadow 160ms ease, transform 160ms ease,
              border-color 160ms ease;
}
.card:hover, .card:focus-within {
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
  transform: translateY(-2px);
}
.card__media {
  aspect-ratio: 16 / 9;
  background: var(--accent-soft); /* placeholder color when image missing */
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  font-size: var(--fs-sm);
}
.card__media img {
  width: 100%; height: 100%; object-fit: cover;
}
.card__body { padding: var(--space-6); flex: 1; display: flex; flex-direction: column; }
.card__body h3 { margin-bottom: var(--space-2); }
.card__body p { color: var(--muted); font-size: var(--fs-sm); }
.card__tags { margin: var(--space-3) 0 var(--space-4); }
.card__link {
  margin-top: auto;
  font-weight: 600;
  font-size: var(--fs-sm);
}

/* Sticky top nav — collapses to hamburger below 720px. */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(250, 250, 247, 0.92);
  -webkit-backdrop-filter: saturate(140%) blur(8px);
  backdrop-filter: saturate(140%) blur(8px);
  border-bottom: 1px solid var(--border);
  height: var(--nav-h);
}
.nav__inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
}
.nav__brand {
  font-weight: 700;
  color: var(--text);
  font-size: var(--fs-lg);
}
.nav__brand:hover { color: var(--text); text-decoration: none; }

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-6);
  list-style: none;
  margin: 0; padding: 0;
}
.nav__links a {
  color: var(--text);
  font-size: var(--fs-sm);
  font-weight: 500;
}
.nav__links a:hover, .nav__links a.is-active {
  color: var(--accent-hover);
  text-decoration: none;
}
.nav__toggle {
  display: none;          /* visible only on mobile via media query */
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: var(--space-2);
  cursor: pointer;
}
.nav__toggle span {
  display: block;
  width: 22px; height: 2px;
  background: var(--text);
  margin: 4px 0;
}

/* Inline SVG icon link (GitHub, email, etc.). */
.icon-link {
  display: inline-flex; align-items: center; gap: var(--space-2);
  color: var(--text);
  font-weight: 500;
}
.icon-link svg { width: 20px; height: 20px; }
.icon-link:hover { color: var(--accent-hover); text-decoration: none; }


/* 6. Section styles ---------------------------------------------------------- */

/* Hero — top of the home page. */
.hero {
  padding: var(--space-24) 0 var(--space-16);
}
.hero__eyebrow {
  color: var(--accent);
  font-size: var(--fs-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-3);
}
.hero h1 { margin-bottom: var(--space-4); }
.hero__tagline {
  font-size: var(--fs-lg);
  color: var(--muted);
  max-width: 60ch;
  margin-bottom: var(--space-8);
}
.hero__ctas {
  display: flex; flex-wrap: wrap; gap: var(--space-3);
}

/* About — bio + education stacked on mobile, two columns on desktop. */
.about__grid {
  display: grid;
  gap: var(--space-12);
  grid-template-columns: 1fr;
}
.about__edu h3 { margin-bottom: var(--space-1); }
.about__edu .meta { color: var(--muted); font-size: var(--fs-sm); margin-bottom: var(--space-4); }

/* Skills — four labeled groups. */
.skills__grid {
  display: grid;
  gap: var(--space-6);
  grid-template-columns: 1fr;
}
.skills__group h3 {
  font-size: var(--fs-base);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin-bottom: var(--space-3);
}

/* Projects grid — Featured Projects on home, and the full grid on projects.html. */
.projects__grid {
  display: grid;
  gap: var(--space-6);
  grid-template-columns: 1fr;
}
.projects__footer {
  margin-top: var(--space-8);
  text-align: center;
}

/* Experience — vertical timeline-style entries. */
.experience__list {
  list-style: none; padding: 0; margin: 0;
  display: grid; gap: var(--space-6);
}
.exp-item {
  padding: var(--space-6);
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent); /* accent stripe on left edge */
  border-radius: var(--radius-md);
}
.exp-item__head {
  display: flex; flex-wrap: wrap;
  justify-content: space-between;
  align-items: baseline;
  gap: var(--space-2);
  margin-bottom: var(--space-1);
}
.exp-item__role { font-weight: 700; }
.exp-item__dates { color: var(--muted); font-size: var(--fs-sm); }
.exp-item__meta { color: var(--muted); font-size: var(--fs-sm); margin-bottom: var(--space-3); }
.exp-item ul { margin: 0; padding-left: var(--space-6); }
.exp-item li { margin-bottom: var(--space-2); }

/* Honors & Involvement — same look as experience entries. */
.honors__list { list-style: none; padding: 0; margin: 0; display: grid; gap: var(--space-6); }

/* Contact. */
.contact__avail {
  color: var(--muted);
  margin-bottom: var(--space-6);
}
.contact__list {
  display: flex; flex-wrap: wrap; gap: var(--space-6);
  list-style: none; margin: 0; padding: 0;
}

/* Footer. */
.footer {
  padding: var(--space-8) 0;
  text-align: center;
  color: var(--muted);
  font-size: var(--fs-sm);
  border-top: 1px solid var(--border);
}
.footer a { color: var(--muted); }
.footer a:hover { color: var(--accent-hover); }


/* 7. Responsive breakpoints -------------------------------------------------- */

/* Tablet / desktop: 720px and up. */
@media (min-width: 720px) {
  .hero h1 { font-size: var(--fs-3xl); }

  .about__grid       { grid-template-columns: 1.4fr 1fr; }
  .skills__grid      { grid-template-columns: repeat(2, 1fr); }
  .projects__grid    { grid-template-columns: repeat(2, 1fr); }
}

/* Wider desktop: 1000px and up — projects shift to 3-up. */
@media (min-width: 1000px) {
  .projects__grid { grid-template-columns: repeat(3, 1fr); }
}

/* Mobile: hide nav links, show hamburger. JS toggles .is-open on .nav__links. */
@media (max-width: 719px) {
  .nav__toggle { display: block; }
  .nav__links {
    position: absolute;
    top: var(--nav-h); left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: var(--space-3) var(--space-6);
    display: none;
  }
  .nav__links.is-open { display: flex; }
  .nav__links li { padding: var(--space-3) 0; border-bottom: 1px solid var(--border); }
  .nav__links li:last-child { border-bottom: none; }

  .hero h1 { font-size: var(--fs-2xl); }
  .hero { padding: var(--space-16) 0 var(--space-12); }
  .section { padding: var(--space-12) 0; }
}