/* ============================================================
   tahmida.com — Clean data-driven portfolio
   System fonts only, no external requests. Light theme.
   ============================================================ */

:root {
  --accent: #0f766e;          /* teal 700 */
  --accent-soft: #14b8a6;     /* teal 500 */
  --accent-wash: #ecfdf9;
  --ink: #0f172a;             /* slate 900 */
  --ink-2: #334155;           /* slate 700 */
  --muted: #64748b;           /* slate 500 */
  --line: #e2e8f0;            /* slate 200 */
  --bg: #ffffff;
  --bg-alt: #f8fafc;          /* slate 50 */
  --ph: #b45309;              /* amber for placeholders */
  --ph-bg: #fffbeb;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(15,23,42,.06), 0 8px 24px rgba(15,23,42,.06);
  --maxw: 1080px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3 { line-height: 1.15; letter-spacing: -0.02em; margin: 0; }

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

.accent { color: var(--accent); }

/* ---- Skip link & focus ---- */
.skip-link {
  position: absolute; left: -999px; top: 0;
  background: var(--accent); color: #fff; padding: .6rem 1rem;
  border-radius: 0 0 8px 0; z-index: 100;
}
.skip-link:focus { left: 0; }

:focus-visible {
  outline: 3px solid var(--accent-soft);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ============ NAV ============ */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.85);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav {
  max-width: var(--maxw); margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  padding: .8rem 1.25rem;
}
.nav__brand {
  display: flex; align-items: center; gap: .55rem;
  font-weight: 700; color: var(--ink); letter-spacing: -0.02em;
}
.nav__brand:hover { text-decoration: none; }
.nav__mark {
  display: grid; place-items: center;
  width: 30px; height: 30px; border-radius: 8px;
  background: var(--accent); color: #fff; font-weight: 800; font-size: .95rem;
}
.nav__menu {
  display: flex; gap: 1.4rem; list-style: none; margin: 0; padding: 0;
}
.nav__menu a { color: var(--ink-2); font-weight: 500; font-size: .95rem; }
.nav__menu a:hover { color: var(--accent); text-decoration: none; }

.nav__toggle {
  display: none; flex-direction: column; gap: 5px;
  background: none; border: 0; cursor: pointer; padding: 8px;
}
.nav__toggle span {
  width: 24px; height: 2px; background: var(--ink); border-radius: 2px;
  transition: transform .25s, opacity .25s;
}
.nav__toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ============ HERO ============ */
.hero {
  background:
    radial-gradient(120% 120% at 90% -10%, var(--accent-wash) 0%, transparent 55%),
    var(--bg);
  border-bottom: 1px solid var(--line);
}
.hero__inner {
  max-width: var(--maxw); margin: 0 auto;
  padding: clamp(3.5rem, 9vw, 7rem) 1.25rem clamp(3rem, 7vw, 5rem);
}
.hero__eyebrow {
  color: var(--accent); font-weight: 600; letter-spacing: .04em;
  text-transform: uppercase; font-size: .8rem; margin: 0 0 1rem;
}
.hero__title {
  font-size: clamp(2.4rem, 6.5vw, 4.2rem); font-weight: 800; margin: 0;
}
.hero__lede {
  font-size: clamp(1.05rem, 2.4vw, 1.3rem); color: var(--ink-2);
  max-width: 42ch; margin: 1.3rem 0 2rem;
}
.hero__actions { display: flex; flex-wrap: wrap; gap: .75rem; }

.hero__chart {
  display: flex; align-items: flex-end; gap: 10px;
  height: 90px; margin-top: 3rem;
}
.hero__chart span {
  flex: 1; max-width: 46px;
  height: var(--h);
  background: linear-gradient(180deg, var(--accent-soft), var(--accent));
  border-radius: 6px 6px 3px 3px;
  transform-origin: bottom; transform: scaleY(0);
  animation: grow .9s cubic-bezier(.2,.7,.3,1) forwards;
}
.hero__chart span:nth-child(1){animation-delay:.05s}
.hero__chart span:nth-child(2){animation-delay:.10s}
.hero__chart span:nth-child(3){animation-delay:.15s}
.hero__chart span:nth-child(4){animation-delay:.20s}
.hero__chart span:nth-child(5){animation-delay:.25s}
.hero__chart span:nth-child(6){animation-delay:.30s}
.hero__chart span:nth-child(7){animation-delay:.35s}
.hero__chart span:nth-child(8){animation-delay:.40s}
@keyframes grow { to { transform: scaleY(1); } }

/* ============ BUTTONS ============ */
.btn {
  display: inline-flex; align-items: center; gap: .4rem;
  padding: .7rem 1.25rem; border-radius: 999px;
  font-weight: 600; font-size: .95rem;
  border: 1px solid var(--line); background: #fff; color: var(--ink);
  transition: transform .15s, box-shadow .15s, background .15s, border-color .15s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); box-shadow: var(--shadow); }
.btn--primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn--primary:hover { background: #0b5d56; }
.btn--ghost { background: transparent; }
.btn[aria-disabled="true"] { opacity: .55; cursor: not-allowed; }

/* ============ SECTIONS ============ */
.section { padding: clamp(3rem, 7vw, 5.5rem) 0; }
.section--alt { background: var(--bg-alt); }
.section__inner { max-width: var(--maxw); margin: 0 auto; padding: 0 1.25rem; }
.section__marker {
  color: var(--accent); font-weight: 700; font-size: .85rem;
  letter-spacing: .08em; margin: 0 0 .4rem;
}
.section__title {
  font-size: clamp(1.7rem, 4vw, 2.4rem); font-weight: 800; margin: 0 0 1.75rem;
}
.note { color: var(--muted); font-size: .9rem; margin-top: 1.25rem; }

/* ---- placeholder marker ---- */
.ph, .chip--ph span {
  background: var(--ph-bg); color: var(--ph);
  border: 1px dashed var(--ph); border-radius: 6px;
  padding: .05em .4em; font-size: .85em; font-weight: 600;
  text-decoration: none;
}
mark.ph { display: inline; }

/* ============ ABOUT ============ */
.about { display: grid; grid-template-columns: 1.6fr 1fr; gap: 2.5rem; align-items: start; }
.about p { font-size: 1.1rem; color: var(--ink-2); margin: 0; }
.about__facts { list-style: none; margin: 0; padding: 0; display: grid; gap: .9rem; }
.about__facts li {
  padding: .9rem 1.1rem; background: #fff; border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
}
.about__facts strong { display: block; color: var(--accent); font-size: .78rem; text-transform: uppercase; letter-spacing: .05em; }

/* ============ SKILLS ============ */
.skills { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
.skills__group h3 { font-size: 1rem; margin-bottom: .9rem; color: var(--ink); }
.chips { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: .5rem; }
.chips li {
  background: #fff; border: 1px solid var(--line); border-radius: 999px;
  padding: .4rem .85rem; font-size: .9rem; font-weight: 500; color: var(--ink-2);
}
.chips .chip--ph { border-style: dashed; color: var(--muted); }

/* ============ CARDS ============ */
.cards { list-style: none; margin: 0; padding: 0; display: grid; gap: 1.25rem; grid-template-columns: repeat(2, 1fr); }
.cards--projects { grid-template-columns: repeat(3, 1fr); }
.card {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.4rem; box-shadow: var(--shadow);
  transition: transform .18s, box-shadow .18s;
}
.card:hover { transform: translateY(-3px); box-shadow: 0 12px 30px rgba(15,23,42,.10); }
.card__title { font-size: 1.15rem; margin-bottom: .35rem; }
.card__meta { color: var(--muted); font-size: .9rem; margin: 0; }
.card__desc { color: var(--ink-2); font-size: .96rem; margin: .4rem 0 1rem; }

.card--cert { display: grid; grid-template-columns: auto 1fr; gap: 1rem; align-items: center; }
.card--cert .card__title { grid-column: 2; }
.card--cert .card__meta { grid-column: 2; }
.card__badge {
  grid-row: 1 / span 2; width: 44px; height: 44px; border-radius: 12px;
  display: grid; place-items: center; font-weight: 800; font-size: 1.3rem;
  background: var(--accent-wash); color: var(--accent);
}

.card__tags { list-style: none; display: flex; flex-wrap: wrap; gap: .4rem; padding: 0; margin: 0 0 1rem; }
.card__tags li { font-size: .78rem; color: var(--accent); background: var(--accent-wash); padding: .2rem .6rem; border-radius: 999px; }
.card__link { font-weight: 600; font-size: .92rem; }

/* ============ TIMELINE ============ */
.timeline { list-style: none; margin: 0; padding: 0; position: relative; }
.timeline::before {
  content: ""; position: absolute; left: 7px; top: 6px; bottom: 6px;
  width: 2px; background: var(--line);
}
.timeline__item { display: grid; grid-template-columns: auto 1fr; gap: 1.1rem; padding-bottom: 1.75rem; position: relative; }
.timeline__item:last-child { padding-bottom: 0; }
.timeline__dot {
  width: 16px; height: 16px; border-radius: 50%;
  background: #fff; border: 3px solid var(--accent); margin-top: 5px; z-index: 1;
}
.timeline__item h3 { font-size: 1.1rem; }
.timeline__meta { color: var(--accent); font-weight: 600; font-size: .88rem; margin: .1rem 0 .4rem; }
.timeline__item p:last-child { color: var(--ink-2); margin: 0; }

/* ============ CONTACT ============ */
.section--contact { background: var(--ink); color: #fff; }
.section--contact .section__marker { color: var(--accent-soft); }
.section--contact .section__title { color: #fff; }
.contact__lede { color: #cbd5e1; font-size: 1.15rem; max-width: 46ch; margin: 0 0 1.75rem; }
.contact__actions { display: flex; flex-wrap: wrap; gap: .75rem; }
.section--contact .btn { background: rgba(255,255,255,.08); border-color: rgba(255,255,255,.2); color: #fff; }
.section--contact .btn:hover { background: rgba(255,255,255,.16); }
.section--contact .btn--primary { background: var(--accent-soft); border-color: var(--accent-soft); color: #06251f; }
.section--contact .btn--primary:hover { background: #0fcdb3; }

/* ============ FOOTER ============ */
.site-footer {
  max-width: var(--maxw); margin: 0 auto;
  padding: 2rem 1.25rem; display: flex; justify-content: space-between; align-items: center;
  color: var(--muted); font-size: .9rem; flex-wrap: wrap; gap: .75rem;
}

/* ============ SCROLL REVEAL ============ */
.reveal { opacity: 0; transform: translateY(18px); transition: opacity .6s ease, transform .6s ease; }
.reveal.is-visible { opacity: 1; transform: none; }

/* ============ RESPONSIVE ============ */
@media (max-width: 820px) {
  .about { grid-template-columns: 1fr; }
  .skills { grid-template-columns: 1fr; }
  .cards, .cards--projects { grid-template-columns: 1fr; }

  .nav__toggle { display: flex; }
  .nav__menu {
    position: absolute; top: 100%; left: 0; right: 0;
    flex-direction: column; gap: 0;
    background: #fff; border-bottom: 1px solid var(--line);
    padding: .5rem 1.25rem 1rem;
    max-height: 0; overflow: hidden; transition: max-height .28s ease;
  }
  .nav__menu.is-open { max-height: 360px; }
  .nav__menu li { border-top: 1px solid var(--line); }
  .nav__menu a { display: block; padding: .85rem 0; }
}

/* ============ REDUCED MOTION ============ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .reveal { opacity: 1; transform: none; }
  .hero__chart span { transform: scaleY(1); }
}