/* ============================================================
   Shared design tokens & base styles
   Ali Haider — optimizer077.github.io
   ============================================================ */

/* ----- Tokens ----- */
:root {
  /* Accent — rich indigo (feels academic, distinctive, not generic-corporate-blue) */
  --clr-accent:        #4f46e5;  /* indigo-600 */
  --clr-accent-dark:   #4338ca;  /* indigo-700 */
  --clr-accent-light:  #eef2ff;  /* indigo-50  */
  --clr-accent-border: #c7d2fe;  /* indigo-200 */

  /* Neutrals */
  --clr-primary:  #1e1b4b;  /* indigo-950 — deep, authoritative, not plain black */
  --clr-text:     #374151;  /* gray-700  */
  --clr-muted:    #6b7280;  /* gray-500  */
  --clr-bg:       #ffffff;
  --clr-bg-alt:   #f9f8ff;  /* very faint indigo tint — subtle warmth */
  --clr-border:   #e8e7f0;  /* lavender-tinted border */

  /* Badges */
  --clr-badge-green:        #dcfce7;  --clr-badge-green-text:  #15803d;
  --clr-badge-blue:         #e0e7ff;  --clr-badge-blue-text:   #3730a3;  /* indigo tones */
  --clr-badge-purple:       #fae8ff;  --clr-badge-purple-text: #86198f;
  --clr-badge-amber:        #fef3c7;  --clr-badge-amber-text:  #92400e;
  --clr-badge-teal:         #ccfbf1;  --clr-badge-teal-text:   #0f766e;

  --radius:    8px;
  --radius-sm: 5px;
  --shadow-sm: 0 1px 3px rgba(79,70,229,.07), 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 16px rgba(79,70,229,.10);

  --fs-xs:   0.78rem;
  --fs-sm:   0.875rem;
  --fs-base: 1rem;
  --fs-lg:   1.1rem;
  --fs-xl:   1.4rem;
  --fs-2xl:  1.75rem;
  --fs-3xl:  2.25rem;

  --max-w:    860px;
  --header-h: 51px;
}

/* ----- Reset ----- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ----- Base ----- */
html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%; /* prevent iOS font inflation */
  text-size-adjust: 100%;
}

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
               Helvetica, Arial, sans-serif;
  font-size: var(--fs-base);
  line-height: 1.7;
  color: var(--clr-text);
  background: var(--clr-bg);
  overflow-x: hidden; /* prevent horizontal scroll on mobile */
}

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

/* ----- Typography ----- */
h1, h2, h3 { color: var(--clr-primary); font-weight: 700; line-height: 1.25; }
h1 { font-size: var(--fs-3xl); }
h2 { font-size: var(--fs-xl); }
h3 { font-size: var(--fs-lg); }

p { margin-bottom: .9rem; }
p:last-child { margin-bottom: 0; }

a { color: var(--clr-accent); text-decoration: none; }
a:hover { text-decoration: underline; color: var(--clr-accent-dark); }

ul { padding-left: 1.25rem; }
li { margin-bottom: .45rem; }

/* ----- Sticky site header / nav ----- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 3px solid var(--clr-accent);   /* distinctive brand stripe */
  border-bottom: 1px solid var(--clr-border);
  padding: .65rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.site-header .logo {
  font-weight: 800;
  font-size: var(--fs-base);
  color: var(--clr-primary);
  text-decoration: none;
  white-space: nowrap;
  letter-spacing: -.01em;
}
.site-header .logo:hover { text-decoration: none; color: var(--clr-accent); }

.site-header nav {
  display: flex;
  align-items: center;
  gap: .35rem;
  flex-wrap: wrap;
}

.site-header nav a {
  font-size: var(--fs-sm);
  color: var(--clr-text);
  padding: .3rem .75rem;
  border-radius: 20px;
  border: 1px solid transparent;
  transition: all .18s;
  white-space: nowrap;
  font-weight: 500;
}
.site-header nav a:hover,
.site-header nav a.active {
  background: var(--clr-accent-light);
  border-color: var(--clr-accent);
  color: var(--clr-accent);
  text-decoration: none;
}

/* ----- Hamburger (mobile nav toggle) ----- */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--clr-primary);
  font-size: 1.35rem;
  line-height: 1;
  /* ensure 44×44 tap target */
  min-width: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  padding: 0;
  transition: background .15s;
  flex-shrink: 0;
}
.nav-toggle:hover { background: var(--clr-bg-alt); }

/* Mobile nav: shown via hamburger */
@media (max-width: 520px) {
  .nav-toggle { display: flex; }

  .site-header {
    position: sticky;   /* keep it sticky so nav dropdown stays in flow */
  }

  /* Nav slides down from header on mobile */
  .site-header nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0; right: 0;
    background: rgba(255,255,255,.98);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--clr-border);
    padding: .6rem .75rem .8rem;
    flex-direction: column;
    align-items: stretch;
    gap: .2rem;
    box-shadow: var(--shadow-md);
    z-index: 200;
  }
  body.nav-open .site-header nav {
    display: flex;
  }
  .site-header nav a {
    padding: .65rem 1rem;
    font-size: var(--fs-base);
    border-radius: var(--radius-sm);
    /* ensure minimum tap target */
    min-height: 44px;
    display: flex;
    align-items: center;
  }
}

/* ----- Page wrapper ----- */
.page-wrap {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 2.5rem 1.25rem 5rem;
}

/* ----- Section card ----- */
.card {
  background: var(--clr-bg);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 1.6rem 1.5rem;
  margin-bottom: 2rem;
  transition: box-shadow .2s;
}

.card h2 {
  font-size: var(--fs-xl);
  color: var(--clr-primary);
  padding-bottom: .5rem;
  margin-bottom: 1.1rem;
  border-bottom: 2px solid var(--clr-accent);
  display: flex;
  align-items: center;
  gap: .5rem;
}

/* ----- Badge / pill ----- */
.badge {
  display: inline-block;
  font-size: var(--fs-xs);
  font-weight: 600;
  padding: .18rem .55rem;
  border-radius: 20px;
  vertical-align: middle;
  white-space: nowrap;
}
.badge-green  { background: var(--clr-badge-green);  color: var(--clr-badge-green-text); }
.badge-blue   { background: var(--clr-badge-blue);   color: var(--clr-badge-blue-text); }
.badge-purple { background: var(--clr-badge-purple); color: var(--clr-badge-purple-text); }
.badge-amber  { background: var(--clr-badge-amber);  color: var(--clr-badge-amber-text); }

/* ----- Tag chips (research interests etc.) ----- */
.tags { display: flex; flex-wrap: wrap; gap: .45rem; margin-top: .5rem; }
.tag {
  font-size: var(--fs-sm);
  background: var(--clr-accent-light);
  color: var(--clr-accent-dark);
  border: 1px solid var(--clr-accent-border);
  padding: .28rem .8rem;
  border-radius: 20px;
  font-weight: 500;
  letter-spacing: .01em;
}

/* ----- Footer ----- */
.site-footer {
  margin-top: 3rem;
  padding: 1.25rem 1.5rem;
  border-top: 1px solid var(--clr-border);
  font-size: var(--fs-sm);
  color: var(--clr-muted);
  text-align: center;
  background: var(--clr-bg-alt);
  letter-spacing: .01em;
}

/* ----- Responsive ----- */
@media (max-width: 600px) {
  h1 { font-size: var(--fs-2xl); }
  .site-header { padding: .55rem .85rem; }
  .page-wrap { padding: 1.5rem .9rem 4rem; }
  .card { padding: 1.2rem 1rem; }
}

/* Ensure all interactive elements meet 44px tap target on touch devices */
@media (pointer: coarse) {
  a, button {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
  }
  /* override for inline links inside paragraphs */
  p a, li a, .pub-authors a, .about-text a {
    min-height: unset;
    display: inline;
  }
}