/* ===================================================================
   TANJIM MAHBUB — PORTFOLIO STYLESHEET (v2)
   Design language: "Engineering Logbook" — an editorial, document-led
   layout. Warm paper surface, near-black ink, deep engineering green
   for action, muted bronze reserved for dates/achievement metadata.
   No cards, no gradients, no glassmorphism. Hairline rules carry the
   structure. One signature graphic: the annotated schematic in the hero.
   =================================================================== */

/* ---------- TOKENS ---------- */
:root {
  --ink: #14181F;
  --ink-soft: #4A5160;
  --muted: #8B8F7E;
  --paper: #FAFAF7;
  --paper-dim: #F1EEE6;
  --line: #DEDAD0;
  --line-strong: #C8C3B6;
  --accent: #1F4D3D;
  --accent-soft: #E7EDE7;
  --bronze: #8A6D3B;

  --font-display: 'Source Serif 4', Georgia, 'Times New Roman', serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'IBM Plex Mono', 'SF Mono', monospace;

  --measure: 680px;
  --measure-wide: 1040px;

  --fs-hero: clamp(2.75rem, 7vw, 5.5rem);
  --fs-h2: clamp(1.85rem, 3.4vw, 2.65rem);
  --fs-h3: clamp(1.15rem, 1.8vw, 1.4rem);
  --fs-lede: clamp(1.05rem, 1.6vw, 1.2rem);

  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --t-fast: 0.18s;
  --t-med: 0.4s;
}

/* ---------- RESET ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-body);
  background: var(--paper);
  color: var(--ink);
  font-size: 1rem;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
img { display: block; max-width: 100%; height: auto; }
a { color: inherit; text-decoration: none; }
button { font: inherit; background: none; border: none; cursor: pointer; color: inherit; }

::selection { background: var(--accent); color: var(--paper); }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

a:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

/* ---------- LAYOUT PRIMITIVES ---------- */
.section-spine {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 0 1.5rem;
}
.section-head-full {
  max-width: var(--measure-wide);
  margin: 0 auto;
  padding: 0 1.5rem;
}
.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--bronze);
  margin-bottom: 1rem;
}
.section-title {
  font-family: var(--font-display);
  font-size: var(--fs-h2);
  font-weight: 500;
  line-height: 1.2;
  letter-spacing: -0.01em;
  margin-bottom: 2.5rem;
}

section { padding: clamp(4.5rem, 9vw, 7.5rem) 0; border-bottom: 1px solid var(--line); }
section:last-of-type { border-bottom: none; }

/* Reveal-on-scroll: subtle, no slide-bounce */
.will-reveal { opacity: 0; transform: translateY(14px); transition: opacity 0.7s var(--ease), transform 0.7s var(--ease); }
.will-reveal.is-visible { opacity: 1; transform: translateY(0); }

/* ---------- SCROLL PROGRESS (hairline, restrained) ---------- */
.progress {
  position: fixed; top: 0; left: 0; height: 2px; width: 0%;
  background: var(--accent); z-index: 1000; transition: width 0.1s linear;
}

/* ---------- MASTHEAD ---------- */
.masthead {
  position: fixed; top: 0; left: 0; right: 0; z-index: 900;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--t-med) var(--ease);
}
.masthead.is-scrolled { border-color: var(--line); }
.masthead__row {
  max-width: var(--measure-wide);
  margin: 0 auto;
  padding: 1.35rem 1.5rem;
  display: flex; align-items: center; justify-content: space-between;
}
.masthead__name {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 600;
}
.masthead__nav { display: flex; gap: 2.25rem; }
.masthead__nav a {
  font-size: 0.88rem; color: var(--ink-soft);
  position: relative;
  transition: color var(--t-fast);
}
.masthead__nav a::after {
  content: ''; position: absolute; left: 0; right: 0; bottom: -6px; height: 1px;
  background: var(--accent); transform: scaleX(0); transition: transform var(--t-fast) var(--ease);
}
.masthead__nav a:hover { color: var(--ink); }
.masthead__nav a:hover::after { transform: scaleX(1); }

.masthead__menu-btn {
  display: none; flex-direction: column; justify-content: center; gap: 5px;
  width: 28px; height: 28px;
}
.masthead__menu-btn span { display: block; height: 1px; background: var(--ink); width: 100%; transition: transform var(--t-fast) var(--ease), opacity var(--t-fast); }
.masthead__menu-btn.is-active span:first-child { transform: translateY(2.5px) rotate(45deg); }
.masthead__menu-btn.is-active span:last-child { transform: translateY(-2.5px) rotate(-45deg); }

.mobile-menu {
  position: fixed; inset: 0; top: 0; z-index: 850;
  background: var(--paper);
  display: flex; flex-direction: column; justify-content: center; gap: 0;
  padding: 0 2rem;
  transform: translateY(-8px);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--t-med) var(--ease), transform var(--t-med) var(--ease), visibility var(--t-med);
}
.mobile-menu.is-open { opacity: 1; visibility: visible; transform: translateY(0); }
.mobile-menu a {
  font-family: var(--font-display);
  font-size: 2.1rem;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--line);
}

/* ---------- HERO ---------- */
.hero { padding-top: clamp(7rem, 14vw, 10rem); border-bottom: 1px solid var(--line); }
.hero__grid {
  max-width: var(--measure-wide);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: grid;
  grid-template-columns: 1.5fr 1fr;
  gap: clamp(2.5rem, 6vw, 5rem);
  align-items: center;
}
.hero__location {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  color: var(--muted);
  margin-bottom: 1.5rem;
}
.hero__name {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: var(--fs-hero);
  line-height: 1.02;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
}
.hero__role {
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(1.2rem, 2vw, 1.5rem);
  color: var(--accent);
  margin-bottom: 1.5rem;
}
.hero__lede {
  font-size: var(--fs-lede);
  color: var(--ink-soft);
  max-width: 42ch;
  margin-bottom: 2.5rem;
}
.hero__actions { display: flex; gap: 2.5rem; flex-wrap: wrap; }

.link-arrow {
  font-weight: 600; font-size: 0.95rem;
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding-bottom: 0.3rem; border-bottom: 1.5px solid var(--ink);
  transition: gap var(--t-fast), border-color var(--t-fast), color var(--t-fast);
}
.link-arrow:hover { gap: 0.85rem; border-color: var(--accent); color: var(--accent); }
.link-arrow--quiet { border-color: var(--line-strong); color: var(--ink-soft); }
.link-arrow--quiet:hover { border-color: var(--accent); color: var(--accent); }
.link-arrow__glyph { transition: transform var(--t-fast) var(--ease); }
.link-arrow:hover .link-arrow__glyph { transform: translateX(2px); }

.hero__portrait { display: flex; justify-content: center; }
.portrait-frame {
  width: 100%; max-width: 320px; aspect-ratio: 4 / 5;
  background: var(--paper-dim);
  border: 1px solid var(--line);
  overflow: hidden;
}
.portrait-frame__img { width: 100%; height: 100%; object-fit: cover; }

/* Hero highlights — instant credibility strip below hero text */
.hero__highlights {
  max-width: var(--measure-wide);
  margin: clamp(2.5rem, 5vw, 3.5rem) auto 0;
  padding: 0 1.5rem;
}
.highlights-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: clamp(1.25rem, 3vw, 2rem);
  padding-top: 1.75rem;
  border-top: 1px solid var(--line);
}
.highlights-row__item dt {
  font-family: var(--font-mono); font-size: 0.7rem; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--bronze); margin-bottom: 0.4rem;
}
.highlights-row__item dd { font-size: 0.92rem; font-weight: 600; color: var(--ink); line-height: 1.35; }

/* Hero schematic — the signature element, appears once */
.hero__schematic {
  max-width: var(--measure-wide);
  margin: clamp(3rem, 6vw, 5rem) auto 0;
  padding: 0 1.5rem 3rem;
}
.schematic-svg { width: 100%; height: auto; max-height: 160px; }
.sch-line { stroke: var(--ink-soft); stroke-width: 1.2; fill: none; }
.sch-line--thin { stroke: var(--line-strong); stroke-width: 1; }
.sch-node { fill: var(--accent); }
.sch-node--end { fill: var(--bronze); }
.sch-label {
  font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.04em;
  fill: var(--muted); text-transform: uppercase;
}
.schematic-svg path, .schematic-svg line {
  stroke-dasharray: 1400;
  stroke-dashoffset: 1400;
  animation: drawSchematic 1.8s var(--ease) forwards;
  animation-delay: 0.3s;
}
@keyframes drawSchematic { to { stroke-dashoffset: 0; } }
@media (prefers-reduced-motion: reduce) {
  .schematic-svg path, .schematic-svg line { animation: none; stroke-dashoffset: 0; }
}

/* ---------- ABOUT ---------- */
.about__para {
  font-size: var(--fs-lede);
  color: var(--ink-soft);
  max-width: 60ch;
  margin-bottom: 1.5rem;
}
.about__para:last-child { margin-bottom: 0; }

/* ---------- CURRENT FOCUS ---------- */
.focus { padding-top: clamp(3rem, 6vw, 4.5rem); padding-bottom: clamp(3rem, 6vw, 4.5rem); }
.focus-list {
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.75rem 2rem;
}
.focus-list__item dt {
  font-family: var(--font-mono); font-size: 0.7rem; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--muted); margin-bottom: 0.35rem;
}
.focus-list__item dd { font-size: 0.98rem; font-weight: 500; color: var(--ink); }

/* ---------- HOW I WORK (philosophy) ---------- */
.philosophy { padding-top: clamp(3rem, 6vw, 4.5rem); padding-bottom: clamp(3rem, 6vw, 4.5rem); }
.philosophy__statement {
  font-family: var(--font-display); font-style: italic; font-weight: 500;
  font-size: clamp(1.3rem, 2.4vw, 1.75rem); color: var(--ink);
  max-width: 32ch; line-height: 1.35; margin-bottom: 1.5rem;
}
.philosophy__para { color: var(--ink-soft); max-width: 56ch; margin-bottom: 1rem; font-size: 0.98rem; }
.philosophy__para:last-child { margin-bottom: 0; }
.philosophy__signature {
  color: var(--ink); font-weight: 600; font-size: 1rem;
  padding-top: 1.25rem; border-top: 1px solid var(--line); max-width: 40ch;
}

/* ---------- WORK ---------- */
.work__list {
  max-width: var(--measure-wide);
  margin: 0 auto;
  padding: 0 1.5rem;
}
.work-item {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(2rem, 5vw, 4rem);
  align-items: center;
  padding: clamp(2.5rem, 5vw, 4rem) 0;
  border-bottom: 1px solid var(--line);
}
.work__list .work-item:last-child { border-bottom: none; padding-bottom: 0; }
.work__list .work-item:nth-child(even) .work-item__media { order: 2; }

.work-item__media {
  aspect-ratio: 16 / 11;
  background: var(--paper-dim);
  border: 1px solid var(--line);
  overflow: hidden;
}
.work-item__media img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.6s var(--ease); }
.work-item:hover .work-item__media img { transform: scale(1.02); }

.work-item__meta {
  font-family: var(--font-mono); font-size: 0.72rem; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 0.85rem;
}
.work-item__title {
  font-family: var(--font-display); font-size: var(--fs-h3); font-weight: 600;
  margin-bottom: 0.85rem;
}
.work-item__desc { color: var(--ink-soft); font-size: 0.96rem; margin-bottom: 1rem; max-width: 46ch; }
.work-item__stack { font-family: var(--font-mono); font-size: 0.78rem; color: var(--muted); margin-bottom: 1.1rem; }

.work-item__links { display: flex; gap: 1.5rem; flex-wrap: wrap; }
.link-arrow--sm { font-size: 0.85rem; font-weight: 600; padding-bottom: 0.2rem; border-bottom: 1px solid var(--line-strong); }
.link-arrow--sm:hover { border-color: var(--accent); }

/* Secondary project tier — denser, smaller, visually subordinate */
.work__minor-head {
  max-width: var(--measure-wide); margin: clamp(3rem, 6vw, 4rem) auto 0; padding: 0 1.5rem;
  border-top: 1px solid var(--line); padding-top: 1.75rem;
}
.work__minor-label {
  font-family: var(--font-mono); font-size: 0.72rem; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--muted);
}
.work__minor-grid {
  max-width: var(--measure-wide); margin: 1.75rem auto 0; padding: 0 1.5rem;
  display: grid; grid-template-columns: repeat(3, 1fr); gap: clamp(1.5rem, 3vw, 2.25rem);
}
.work-minor__media {
  aspect-ratio: 4 / 3; background: var(--paper-dim); border: 1px solid var(--line);
  overflow: hidden; margin-bottom: 1rem;
}
.work-minor__media img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.6s var(--ease); }
.work-minor:hover .work-minor__media img { transform: scale(1.03); }
.work-minor__meta {
  font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 0.5rem;
}
.work-minor__title { font-family: var(--font-display); font-size: 1.02rem; font-weight: 600; margin-bottom: 0.45rem; }
.work-minor__desc { color: var(--ink-soft); font-size: 0.85rem; margin-bottom: 0.85rem; }

/* ---------- EXPERIENCE TIMELINE ---------- */
.timeline { margin-top: 0.5rem; }
.timeline__entry {
  display: grid;
  grid-template-columns: 140px 1fr;
  gap: clamp(1.5rem, 3vw, 2.5rem);
  padding: clamp(2rem, 4vw, 2.75rem) 0;
  border-top: 1px solid var(--line);
}
.timeline__entry:first-child { border-top: none; }
.timeline__date {
  font-family: var(--font-mono); font-size: 0.8rem; color: var(--bronze);
  white-space: nowrap;
}
.timeline__date-sep { margin: 0 0.3rem; color: var(--muted); }
.timeline__content h3 {
  font-family: var(--font-display); font-size: var(--fs-h3); font-weight: 600; margin-bottom: 0.3rem;
}
.timeline__org { color: var(--muted); font-size: 0.88rem; margin-bottom: 0.9rem; }
.timeline__content p:not(.timeline__org) { color: var(--ink-soft); font-size: 0.95rem; max-width: 60ch; }

/* ---------- ACHIEVEMENTS ---------- */
.achievement-entry {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: clamp(1.75rem, 3.5vw, 3rem);
  padding: clamp(2.25rem, 4.5vw, 3rem) 0;
  border-top: 1px solid var(--line);
  align-items: start;
}
.achievement-entry:first-of-type { border-top: none; }
.achievement-entry--feature {
  padding-bottom: clamp(2.75rem, 5.5vw, 3.5rem);
  margin-bottom: 0.5rem;
  border-bottom: 1px solid var(--line);
}
.achievement-entry--feature .achievement-entry__date { color: var(--bronze); font-weight: 600; }
.achievement-entry--feature h3 { font-size: clamp(1.3rem, 2.1vw, 1.6rem); }

.achievement-entry__cert {
  aspect-ratio: 4 / 3;
  background: var(--paper-dim);
  border: 1px solid var(--line);
  overflow: hidden;
}
.achievement-entry__cert img { width: 100%; height: 100%; object-fit: cover; }

.achievement-entry__date {
  font-family: var(--font-mono); font-size: 0.78rem; color: var(--bronze); margin-bottom: 0.5rem;
}
.achievement-entry__body h3 {
  font-family: var(--font-display); font-size: var(--fs-h3); font-weight: 600; margin-bottom: 0.3rem;
}
.achievement-entry__org { color: var(--muted); font-size: 0.88rem; margin-bottom: 0.9rem; }
.achievement-entry__body p:not(.achievement-entry__date):not(.achievement-entry__org) {
  color: var(--ink-soft); font-size: 0.95rem; max-width: 58ch;
}

/* ---------- RESEARCH ---------- */
.research__topic {
  font-family: var(--font-display); font-style: italic; font-size: 1.15rem;
  color: var(--ink); max-width: 56ch; margin-bottom: 0.6rem; line-height: 1.4;
}
.research__institution { font-family: var(--font-mono); font-size: 0.8rem; color: var(--muted); margin-bottom: 2rem; }
.research__body p { color: var(--ink-soft); max-width: 62ch; margin-bottom: 1.25rem; }
.research__body p:last-child { margin-bottom: 0; }

.research__facts {
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.5rem;
  margin-top: 2.5rem; padding-top: 2rem; border-top: 1px solid var(--line);
}
.research__fact dt {
  font-family: var(--font-mono); font-size: 0.7rem; letter-spacing: 0.06em; text-transform: uppercase;
  color: var(--muted); margin-bottom: 0.35rem;
}
.research__fact dd { font-size: 0.95rem; font-weight: 500; }

/* ---------- RECENT CODE ---------- */
.code__rows { display: flex; flex-direction: column; }
.code__row {
  display: flex; justify-content: space-between; align-items: baseline; gap: 1.5rem;
  padding: 1.25rem 0; border-top: 1px solid var(--line);
  transition: color var(--t-fast), padding-left var(--t-fast) var(--ease);
}
.code__rows .code__row:last-child { border-bottom: 1px solid var(--line); }
.code__row:hover { color: var(--accent); padding-left: 0.5rem; }
.code__row-main { display: flex; flex-direction: column; gap: 0.3rem; }
.code__row-name { font-family: var(--font-mono); font-weight: 600; font-size: 0.95rem; }
.code__row-desc { font-size: 0.85rem; color: var(--muted); }
.code__row-lang {
  font-family: var(--font-mono); font-size: 0.78rem; color: var(--bronze); white-space: nowrap;
}

/* ---------- CONTACT ---------- */
.contact__lede { color: var(--ink-soft); max-width: 50ch; margin-bottom: 2.5rem; font-size: var(--fs-lede); }
.contact__rows { display: flex; flex-direction: column; }
.contact__row {
  display: flex; justify-content: space-between; align-items: baseline;
  padding: 1.25rem 0; border-top: 1px solid var(--line);
  transition: color var(--t-fast), padding-left var(--t-fast) var(--ease);
}
.contact__rows .contact__row:last-child { border-bottom: 1px solid var(--line); }
.contact__row:hover { color: var(--accent); padding-left: 0.5rem; }
.contact__row-label {
  font-family: var(--font-mono); font-size: 0.78rem; letter-spacing: 0.05em; text-transform: uppercase;
  color: var(--muted);
}
.contact__row-value { font-weight: 600; font-size: 1rem; }

/* ---------- FOOTER ---------- */
.footer { padding: 2.5rem 0 3rem; }
.footer__row {
  max-width: var(--measure-wide); margin: 0 auto; padding: 0 1.5rem;
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 0.75rem;
  font-size: 0.82rem; color: var(--muted);
}

/* ---------- RESPONSIVE ---------- */
@media (max-width: 900px) {
  .masthead__nav { display: none; }
  .masthead__menu-btn { display: flex; }
  .hero__grid { grid-template-columns: 1fr; text-align: left; }
  .hero__portrait { order: -1; justify-content: flex-start; }
  .portrait-frame { max-width: 200px; }
  .highlights-row { grid-template-columns: repeat(2, 1fr); gap: 1.5rem 1.5rem; }
  .work-item { grid-template-columns: 1fr; }
  .work__list .work-item:nth-child(even) .work-item__media { order: 0; }
  .work__minor-grid { grid-template-columns: repeat(2, 1fr); }
  .achievement-entry { grid-template-columns: 140px 1fr; }
}

@media (max-width: 640px) {
  .timeline__entry { grid-template-columns: 1fr; gap: 0.5rem; }
  .achievement-entry { grid-template-columns: 1fr; }
  .achievement-entry__cert { max-width: 220px; }
  .research__facts { grid-template-columns: 1fr 1fr; }
  .hero__actions { gap: 1.5rem; }
  .highlights-row { grid-template-columns: 1fr 1fr; gap: 1.5rem 1.25rem; }
  .focus-list { grid-template-columns: 1fr; }
  .work__minor-grid { grid-template-columns: 1fr; }
  .code__row { flex-direction: column; gap: 0.4rem; align-items: flex-start; }
  .contact__row { flex-direction: column; gap: 0.3rem; align-items: flex-start; }
}