/* ============================================================
   Bilel Khlaifia | portfolio
   Monochrome. No dependencies. No webfonts.
   ============================================================ */

:root {
  --bg:        #ffffff;
  --bg-alt:    #fafafa;
  --fg:        #0a0a0a;
  --fg-muted:  #6b6b6b;
  --fg-faint:  #9a9a9a;
  --line:      #e4e4e4;
  --line-firm: #cfcfcf;
  --inv-bg:    #0a0a0a;
  --inv-fg:    #ffffff;

  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --wrap: 1120px;
  --pad: 28px;
  --r: 3px;
}

[data-theme="dark"] {
  --bg:        #0a0a0a;
  --bg-alt:    #131313;
  --fg:        #fafafa;
  --fg-muted:  #a3a3a3;
  --fg-faint:  #737373;
  --line:      #262626;
  --line-firm: #3d3d3d;
  --inv-bg:    #fafafa;
  --inv-fg:    #0a0a0a;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 76px;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color .25s ease, color .25s ease;
}

img { max-width: 100%; display: block; }

a { color: inherit; }

.wrap {
  width: 100%;
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--pad);
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--fg);
  color: var(--bg);
  padding: 12px 18px;
  z-index: 999;
}
.skip:focus { left: 12px; top: 12px; }

:focus-visible {
  outline: 2px solid var(--fg);
  outline-offset: 3px;
}

/* ---------- header ---------- */

.site-head {
  position: sticky;
  top: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}

.head-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  height: 64px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  text-decoration: none;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 30px; height: 30px;
  background: var(--fg);
  color: var(--bg);
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .02em;
  border-radius: var(--r);
}

.brand-name { font-size: 15px; }

.nav {
  display: flex;
  gap: 26px;
  font-family: var(--mono);
  font-size: 12.5px;
  letter-spacing: .01em;
}

.nav a {
  text-decoration: none;
  color: var(--fg-muted);
  padding: 4px 0;
  border-bottom: 1px solid transparent;
  transition: color .15s ease, border-color .15s ease;
}
.nav a:hover,
.nav a.active { color: var(--fg); border-bottom-color: var(--fg); }

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: none;
  border: 1px solid var(--line-firm);
  color: var(--fg-muted);
  font-family: var(--mono);
  font-size: 11.5px;
  padding: 6px 12px;
  border-radius: 999px;
  cursor: pointer;
  transition: color .15s, border-color .15s;
}
.toggle:hover { color: var(--fg); border-color: var(--fg); }

.toggle-dot {
  width: 9px; height: 9px;
  border-radius: 50%;
  background: var(--fg);
  box-shadow: inset 0 0 0 1px var(--fg);
}
[data-theme="dark"] .toggle-dot { background: transparent; }

/* ---------- hero ---------- */

.hero {
  padding: clamp(72px, 13vw, 148px) 0 clamp(56px, 9vw, 104px);
  border-bottom: 1px solid var(--line);
}

.eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--fg-muted);
  margin: 0 0 22px;
}

.hero-title {
  font-size: clamp(52px, 13vw, 132px);
  line-height: .92;
  letter-spacing: -0.045em;
  font-weight: 700;
  margin: 0 0 32px;
}

.hero-lede {
  max-width: 60ch;
  font-size: clamp(17px, 2.1vw, 21px);
  line-height: 1.6;
  color: var(--fg-muted);
  margin: 0 0 44px;
}

.hero-meta {
  list-style: none;
  padding: 0;
  margin: 0 0 40px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 0;
  border-top: 1px solid var(--line);
}

.hero-meta li {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding: 18px 20px 18px 0;
  border-bottom: 1px solid var(--line);
}

.hero-meta .k,
.contact-card .k {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--fg-faint);
}
.hero-meta .v { font-size: 14.5px; }

.hero-cta { display: flex; flex-wrap: wrap; gap: 11px; }

.btn {
  display: inline-block;
  padding: 11px 22px;
  border: 1px solid var(--line-firm);
  border-radius: var(--r);
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: background-color .15s, color .15s, border-color .15s;
}
.btn:hover { border-color: var(--fg); }

.btn-solid {
  background: var(--fg);
  color: var(--bg);
  border-color: var(--fg);
}
.btn-solid:hover { opacity: .85; }

/* ---------- sections ---------- */

.section { padding: clamp(64px, 9vw, 108px) 0; }
.section.alt { background: var(--bg-alt); border-block: 1px solid var(--line); }

.sec-head {
  display: flex;
  align-items: baseline;
  gap: 16px;
  margin-bottom: 44px;
  padding-bottom: 18px;
  border-bottom: 1px solid var(--line);
}

.sec-num {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--fg-faint);
  letter-spacing: .08em;
}

.sec-head h2 {
  font-size: clamp(26px, 4vw, 38px);
  letter-spacing: -0.03em;
  font-weight: 600;
  margin: 0;
}

.sub {
  font-size: 13px;
  font-family: var(--mono);
  text-transform: uppercase;
  letter-spacing: .13em;
  color: var(--fg);
  margin: 0 0 6px;
  font-weight: 600;
}
.sub-gap { margin-top: 52px; }

.sub-note {
  font-size: 14px;
  color: var(--fg-muted);
  margin: 0 0 26px;
}

/* ---------- grids & cards ---------- */

.grid-4, .grid-3 {
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--r);
  overflow: hidden;
}
.grid-4 { grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); }

.card {
  background: var(--bg);
  padding: 26px 24px;
  transition: background-color .18s ease;
}
.section.alt .card { background: var(--bg-alt); }
.card:hover { background: color-mix(in srgb, var(--fg) 4%, var(--bg)); }

.card h3 {
  font-size: 16px;
  margin: 0 0 10px;
  letter-spacing: -0.01em;
  font-weight: 600;
}
.card h4 {
  font-size: 15px;
  margin: 0;
  letter-spacing: -0.01em;
  font-weight: 600;
}
.card p {
  margin: 10px 0 0;
  font-size: 14px;
  color: var(--fg-muted);
  line-height: 1.6;
}

.tag {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--fg-faint);
  border: 1px solid var(--line-firm);
  padding: 2px 8px;
  border-radius: 999px;
  margin-bottom: 12px;
}

.chips {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding: 0;
  margin: 16px 0 0;
}
.chips li {
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--fg-muted);
  border: 1px solid var(--line);
  padding: 3px 8px;
  border-radius: var(--r);
}

/* repo card */
.repo-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}
.repo-top h4 { font-family: var(--mono); font-size: 13px; word-break: break-word; }
.repo-top a { text-decoration: none; border-bottom: 1px solid var(--line-firm); }
.repo-top a:hover { border-bottom-color: var(--fg); }

.stars {
  flex: none;
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--fg-muted);
  white-space: nowrap;
}
.stars::before { content: "★ "; }

.more { margin: 26px 0 0; font-size: 14px; }
.more a { font-family: var(--mono); font-size: 13px; text-decoration: none; border-bottom: 1px solid var(--line-firm); }
.more a:hover { border-bottom-color: var(--fg); }

/* ---------- featured writing ---------- */

.blog-list { display: grid; gap: 24px; }

.feature-post {
  display: grid;
  grid-template-columns: 350px minmax(0, 1fr);
  align-items: center;
  border: 1px solid var(--line);
  border-radius: var(--r);
  overflow: hidden;
}

.feature-visual {
  display: block;
  width: 300px;
  aspect-ratio: 1;
  margin: 24px auto;
  background: var(--bg-alt);
  border: 1px solid var(--line);
  overflow: hidden;
}

.feature-mosaic {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  width: 100%;
  height: 100%;
  gap: 1px;
  background: var(--line);
}

.feature-tile {
  position: relative;
  min-width: 0;
  overflow: hidden;
  background: var(--bg);
}

.feature-tile img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  background: var(--bg);
  transition: transform .35s ease;
}

.feature-visual:hover img { transform: scale(1.02); }

.feature-chart {
  display: grid;
  place-items: center;
  padding: 12px;
}

.feature-chart > img {
  width: 100%;
  height: auto;
  background: #fff;
}

.feature-image > img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.feature-tile > span {
  position: absolute;
  left: 4px;
  bottom: 4px;
  max-width: calc(100% - 8px);
  padding: 2px 4px;
  overflow: hidden;
  background: color-mix(in srgb, var(--bg) 90%, transparent);
  border: 1px solid var(--line-firm);
  color: var(--fg);
  font: 6.5px/1.2 var(--mono);
  letter-spacing: .03em;
  text-overflow: ellipsis;
  text-transform: uppercase;
  white-space: nowrap;
}

.feature-copy {
  padding: clamp(28px, 4vw, 46px);
  border-left: 1px solid var(--line);
}

.post-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  margin: 0 0 22px;
  color: var(--fg-faint);
  font: 11px/1.5 var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.feature-copy h3 {
  margin: 0;
  font-size: clamp(25px, 3.2vw, 39px);
  line-height: 1.12;
  letter-spacing: -.035em;
}

.feature-copy h3 a { text-decoration: none; }
.feature-copy h3 a:hover { text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 5px; }
.feature-copy > p:not(.post-meta, .more) { margin: 20px 0 0; color: var(--fg-muted); }

/* ---------- research article ---------- */

.article-shell { --article: 760px; }

.article-head {
  padding: clamp(64px, 11vw, 126px) 0 clamp(48px, 8vw, 88px);
  border-bottom: 1px solid var(--line);
}

.article-kicker {
  margin: 0 0 24px;
  color: var(--fg-muted);
  font: 12px/1.5 var(--mono);
  letter-spacing: .14em;
  text-transform: uppercase;
}

.article-title {
  max-width: 1020px;
  margin: 0;
  font-size: clamp(44px, 8vw, 88px);
  line-height: .98;
  letter-spacing: -.05em;
}

.article-deck {
  max-width: 760px;
  margin: 32px 0 0;
  color: var(--fg-muted);
  font-size: clamp(18px, 2.3vw, 22px);
  line-height: 1.55;
}

.article-byline {
  display: flex;
  flex-wrap: wrap;
  gap: 9px 24px;
  margin: 36px 0 0;
  font: 12px/1.5 var(--mono);
  color: var(--fg-faint);
}

.article-layout {
  display: grid;
  grid-template-columns: 190px minmax(0, var(--article));
  justify-content: center;
  gap: 58px;
  padding-block: clamp(54px, 8vw, 92px);
}

.article-toc {
  position: sticky;
  top: 96px;
  align-self: start;
  font: 11.5px/1.5 var(--mono);
}

.article-toc strong { display: block; margin-bottom: 12px; text-transform: uppercase; letter-spacing: .12em; }
.article-toc ol { list-style: none; margin: 0; padding: 0; }
.article-toc li { border-top: 1px solid var(--line); }
.article-toc li:last-child { border-bottom: 1px solid var(--line); }
.article-toc a { display: block; padding: 9px 0; color: var(--fg-muted); text-decoration: none; }
.article-toc a:hover { color: var(--fg); }

.paper h2 {
  margin: 72px 0 20px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
  font-size: clamp(27px, 4vw, 38px);
  line-height: 1.18;
  letter-spacing: -.03em;
}

.paper h2:first-child { margin-top: 0; }
.paper h3 { margin: 34px 0 12px; font-size: 20px; letter-spacing: -.015em; }
.paper p { margin: 0 0 20px; }
.paper a { text-underline-offset: 3px; }
.paper code { overflow-wrap: anywhere; }
.paper ul, .paper ol { margin: 0 0 24px; padding-left: 22px; }
.paper li { margin-bottom: 8px; }
.paper li::marker { color: var(--fg-faint); }

.abstract {
  padding: 28px;
  border: 1px solid var(--line-firm);
  background: var(--bg-alt);
}

.abstract h2 { margin: 0 0 14px; padding: 0; border: 0; font: 600 12px/1.5 var(--mono); letter-spacing: .13em; text-transform: uppercase; }
.abstract p:last-child { margin-bottom: 0; }

.paper-figure {
  width: min(100%, 620px);
  margin: 38px auto;
}

.paper-figure > a { display: block; }
.paper-figure img { width: 100%; height: auto; border: 1px solid var(--line); background: #fff; }
.paper-figure figcaption { margin-top: 11px; color: var(--fg-muted); font-size: 13px; line-height: 1.55; }
.paper-figure figcaption strong { color: var(--fg); }

.figure-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  padding: 1px;
  background: var(--line);
}

.figure-cell {
  position: relative;
  overflow: hidden;
  background: var(--bg);
}

.figure-cell a { display: block; }
.figure-cell img {
  display: block;
  width: 100%;
  height: auto;
  border: 0;
  object-fit: contain;
}
.figure-cell span {
  position: absolute;
  left: 10px;
  bottom: 10px;
  padding: 4px 7px;
  background: color-mix(in srgb, var(--bg) 90%, transparent);
  border: 1px solid var(--line-firm);
  color: var(--fg);
  font: 10px/1.35 var(--mono);
  letter-spacing: .05em;
  text-transform: uppercase;
}

.figure-open {
  display: block;
  margin-top: 8px;
  color: var(--fg-faint);
  font: 10.5px/1.5 var(--mono);
  text-transform: uppercase;
  letter-spacing: .07em;
}

.equation {
  margin: 28px 0;
  padding: 22px;
  overflow-x: auto;
  border-block: 1px solid var(--line);
  font: 15px/1.8 var(--mono);
  text-align: center;
}

.equation.left { text-align: left; }

.definition-list {
  display: grid;
  grid-template-columns: 145px 1fr;
  margin: 26px 0;
  border-top: 1px solid var(--line);
}

.definition-list dt,
.definition-list dd {
  margin: 0;
  padding: 11px 0;
  border-bottom: 1px solid var(--line);
}

.definition-list dt { color: var(--fg); font: 12px/1.55 var(--mono); }
.definition-list dd { color: var(--fg-muted); font-size: 13.5px; }

.table-wrap { margin: 28px 0; overflow-x: auto; border: 1px solid var(--line); }
.paper table { width: 100%; border-collapse: collapse; font-size: 13.5px; }
.paper th, .paper td { padding: 11px 14px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
.paper th { background: var(--bg-alt); font: 600 11px/1.4 var(--mono); letter-spacing: .06em; text-transform: uppercase; }
.paper tr:last-child td { border-bottom: 0; }
.paper td:last-child:not(:first-child), .paper th:last-child:not(:first-child) { text-align: right; }

.callout {
  margin: 30px 0;
  padding: 22px 24px;
  border-left: 3px solid var(--fg);
  background: var(--bg-alt);
}
.callout strong { display: block; margin-bottom: 5px; }
.callout p:last-child { margin-bottom: 0; }

.references { font-size: 13.5px; }
.references li { margin-bottom: 14px; }

.article-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 38px; }

/* ---------- timeline ---------- */

.timeline { list-style: none; padding: 0; margin: 0; }

.timeline > li {
  display: grid;
  grid-template-columns: 210px 1fr;
  gap: 32px;
  padding: 32px 0;
  border-top: 1px solid var(--line);
}
.timeline > li:last-child { border-bottom: 1px solid var(--line); }

.tl-when {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--fg-faint);
  letter-spacing: .04em;
  padding-top: 3px;
}

.tl-what h3 {
  margin: 0 0 3px;
  font-size: 18px;
  letter-spacing: -0.015em;
  font-weight: 600;
}

.org {
  margin: 0 0 14px;
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--fg-muted);
}

.tl-what ul { margin: 0; padding-left: 18px; }
.tl-what li {
  font-size: 14.5px;
  color: var(--fg-muted);
  margin-bottom: 8px;
  line-height: 1.6;
}
.tl-what li::marker { color: var(--fg-faint); }

/* ---------- split / lists ---------- */

.split {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 56px;
}

.plain { list-style: none; padding: 0; margin: 0; }
.plain > li {
  padding: 18px 0;
  border-top: 1px solid var(--line);
}
.plain > li:last-child { border-bottom: 1px solid var(--line); }
.plain strong { display: block; font-size: 15px; font-weight: 600; letter-spacing: -0.01em; }
.plain .muted {
  display: block;
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--fg-faint);
  margin-top: 3px;
}
.plain p { margin: 9px 0 0; font-size: 14px; color: var(--fg-muted); }

.awards { list-style: none; padding: 0; margin: 0; }
.awards li {
  display: grid;
  grid-template-columns: 78px 1fr;
  gap: 14px;
  padding: 13px 0;
  border-top: 1px solid var(--line);
  font-size: 14px;
  color: var(--fg-muted);
}
.awards li:last-child { border-bottom: 1px solid var(--line); }
.awards .yr { font-family: var(--mono); font-size: 11.5px; color: var(--fg-faint); padding-top: 2px; }
.awards strong { color: var(--fg); }

/* ---------- skills ---------- */

.skills { margin: 0; display: grid; gap: 0; }
.skills > div {
  display: grid;
  grid-template-columns: 170px 1fr;
  gap: 24px;
  padding: 16px 0;
  border-top: 1px solid var(--line);
}
.skills > div:last-child { border-bottom: 1px solid var(--line); }
.skills dt {
  font-family: var(--mono);
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: .1em;
  color: var(--fg-faint);
  padding-top: 2px;
}
.skills dd { margin: 0; font-size: 14.5px; color: var(--fg-muted); }

/* ---------- contact ---------- */

.contact-lede {
  max-width: 56ch;
  font-size: clamp(17px, 2vw, 20px);
  color: var(--fg-muted);
  margin: 0 0 36px;
}

.contact-grid {
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--r);
  overflow: hidden;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
}

.contact-card {
  background: var(--bg-alt);
  padding: 22px 24px;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: 5px;
  transition: background-color .18s;
}
.contact-card:hover { background: color-mix(in srgb, var(--fg) 5%, var(--bg-alt)); }
.contact-card .v { font-size: 14.5px; word-break: break-word; }

/* ---------- footer ---------- */

.site-foot {
  border-top: 1px solid var(--line);
  padding: 30px 0;
}
.foot-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px;
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--fg-faint);
}
.foot-inner p { margin: 0; }

/* ---------- responsive ---------- */

@media (max-width: 860px) {
  .nav { display: none; }
  .feature-post { grid-template-columns: 1fr; }
  .feature-visual { width: min(240px, calc(100% - 40px)); margin-block: 24px; justify-self: center; }
  .feature-copy { border-left: 0; border-top: 1px solid var(--line); }
  .article-layout { grid-template-columns: minmax(0, var(--article)); }
  .article-toc { display: none; }
  .timeline > li { grid-template-columns: 1fr; gap: 10px; }
  .split { gap: 40px; }
  .skills > div { grid-template-columns: 1fr; gap: 4px; }
}

@media (max-width: 520px) {
  :root { --pad: 20px; }
  .toggle-text { display: none; }
  .toggle { padding: 8px; }
  .hero-meta { grid-template-columns: 1fr; }
  .article-title { font-size: clamp(40px, 13vw, 60px); }
  .abstract { padding: 22px; }
  .figure-cell span { left: 6px; bottom: 6px; max-width: calc(100% - 12px); font-size: 8.5px; }
  .definition-list { grid-template-columns: 1fr; }
  .definition-list dt { padding-bottom: 2px; border-bottom: 0; }
  .definition-list dd { padding-top: 2px; }
}

/* ---------- motion ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    transition-duration: .001ms !important;
  }
}

/* ---------- print ---------- */

@media print {
  .site-head, .toggle, .hero-cta, .site-foot, .more, .article-toc, .article-actions { display: none !important; }
  body { font-size: 11pt; color: #000; background: #fff; }
  .section, .hero { padding: 14pt 0; border: none; }
  .section.alt { background: none; }
  .grid-3, .grid-4, .contact-grid { background: none; border: none; display: block; }
  .card { break-inside: avoid; padding: 6pt 0; }
  a { text-decoration: none; }
}