/* ==========================================================================
   Nihar Ranjan Sahoo: personal homepage
   Layout: sticky top nav, sticky profile sidebar, single content column.
   Colours live in the custom properties below; dark mode swaps them.
   ========================================================================== */

:root {
  --bg: #ffffff;
  --surface: #f6f7f8;
  --text: #494e52;
  --text-strong: #24292e;
  --muted: #7a8288;
  --border: #eaecee;
  --link: #224b8d;
  --link-hover: #12305f;
  --nav: #6b7378;
  --nav-hover: #24292e;
  --badge-bg: #00369f;
  --badge-text: #ffffff;
  --badge-alt-bg: #eef1f6;
  --badge-alt-text: #3b4a63;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.06);

  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --nav-h: 3.4rem;
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #0f1115;
  --surface: #171a21;
  --text: #d0d4da;
  --text-strong: #eef0f3;
  --muted: #9aa0aa;
  --border: #262a32;
  --link: #8ab4f8;
  --link-hover: #b4cffb;
  --nav: #aab0ba;
  --nav-hover: #ffffff;
  --badge-bg: #1e3a6e;
  --badge-text: #dce8ff;
  --badge-alt-bg: #1d2129;
  --badge-alt-text: #b9c0cc;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4);
  color-scheme: dark;
}

/* ---------- base ---------- */

*, *::before, *::after { box-sizing: border-box; }

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 0.75rem);
  -webkit-text-size-adjust: 100%;
  background: var(--bg);
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.6;
  transition: background-color 0.2s ease, color 0.2s ease;
}

a { color: var(--link); text-decoration: none; }
a:hover { color: var(--link-hover); text-decoration: underline; text-underline-offset: 2px; }
a:focus-visible, button:focus-visible { outline: 2px solid var(--link); outline-offset: 2px; border-radius: 3px; }

strong, b { color: var(--text-strong); font-weight: 650; }
em { font-style: italic; }
img { max-width: 100%; height: auto; }
ul { padding-left: 1.25rem; margin: 0.4rem 0 0.8rem; }
li { margin: 0.3rem 0; }
p { margin: 0 0 0.75rem; }

code {
  font-family: var(--mono);
  font-size: 0.86em;
  padding: 0.1em 0.35em;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 4px;
}

.skip-link {
  position: absolute; left: -999px; top: 0.5rem; z-index: 100;
  padding: 0.4rem 0.8rem; background: var(--bg); border: 1px solid var(--border);
}
.skip-link:focus { left: 0.5rem; }

/* ---------- top navigation ---------- */

.masthead {
  position: sticky; top: 0; z-index: 50;
  background: var(--bg);
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  -webkit-backdrop-filter: saturate(160%) blur(8px);
  backdrop-filter: saturate(160%) blur(8px);
  border-bottom: 1px solid var(--border);
}

.masthead__inner {
  max-width: 1180px; margin: 0 auto; height: var(--nav-h);
  padding: 0 1.25rem; display: flex; align-items: center; gap: 1rem;
}

.masthead__brand {
  font-weight: 700; color: var(--text-strong); white-space: nowrap; margin-right: auto;
}
.masthead__brand:hover { text-decoration: none; color: var(--text-strong); }

.nav { display: flex; align-items: center; }
.nav__list { display: flex; gap: 0.25rem; list-style: none; margin: 0; padding: 0; }
.nav__list li { margin: 0; }
.nav__list a {
  position: relative; display: block; padding: 0.4rem 0.6rem;
  color: var(--nav); font-size: 0.95rem; white-space: nowrap;
}
.nav__list a::after {
  content: ""; position: absolute; left: 0.6rem; right: 0.6rem; bottom: 0.1rem; height: 2px;
  background: currentColor; transform: scaleX(0); transition: transform 0.2s ease;
}
.nav__list a:hover { color: var(--nav-hover); text-decoration: none; }
.nav__list a:hover::after, .nav__list a.is-active::after { transform: scaleX(1); }
.nav__list a.is-active { color: var(--nav-hover); }

.icon-btn {
  display: inline-flex; align-items: center; justify-content: center;
  width: 2.2rem; height: 2.2rem; padding: 0; border: 0; border-radius: 8px;
  background: transparent; color: var(--nav); cursor: pointer;
}
.icon-btn:hover { color: var(--nav-hover); background: var(--surface); }

.theme-toggle .icon-sun { display: none; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

.nav-toggle { display: none; }

/* ---------- page layout ---------- */

.layout {
  max-width: 1180px; margin: 0 auto; padding: 2rem 1.25rem 3rem;
  display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: 3.5rem;
}

/* ---------- sidebar / profile ---------- */

.sidebar { align-self: start; position: sticky; top: calc(var(--nav-h) + 1.5rem); }

.profile__avatar {
  display: block; width: 100%; max-width: 190px; aspect-ratio: 1; object-fit: cover;
  border-radius: 50%; padding: 5px; border: 1px solid var(--border); background: var(--bg);
}
.profile__name { margin: 0.9rem 0 0.35rem; font-size: 1.35rem; line-height: 1.25; color: var(--text-strong); }
.profile__bio { margin: 0 0 1.1rem; font-size: 0.95rem; color: var(--text); }

.profile__links { list-style: none; margin: 0; padding: 0; font-size: 0.95rem; }
.profile__links li { margin: 0 0 0.35rem; display: flex; align-items: center; gap: 0.55rem; }
.profile__links a { color: inherit; }
.profile__links a:hover { color: var(--link); }
.profile__links i { width: 1.15rem; text-align: center; color: var(--muted); }

.profile__icons { display: none; }

/* ---------- content ---------- */

.content { min-width: 0; }

.content h1 {
  margin: 2.4rem 0 1rem; padding-bottom: 0.45rem;
  font-size: 1.55rem; line-height: 1.25; color: var(--text-strong);
  border-bottom: 1px solid var(--border);
}
.content h2 {
  margin: 1.6rem 0 0.4rem; font-size: 1.05rem; color: var(--muted);
  text-transform: uppercase; letter-spacing: 0.06em; font-weight: 650;
}
.content > section:first-child > h1 { margin-top: 0; }

.lead p { font-size: 1.02rem; }

.date { color: var(--muted); font-style: italic; white-space: nowrap; }

.list-tight li { margin: 0.35rem 0; }

.news li .date { display: inline-block; min-width: 4.4rem; font-style: italic; }

.xp li { margin-bottom: 0.9rem; }
.xp .meta { color: var(--muted); }
.xp p { margin: 0.2rem 0 0; }

/* ---------- publications ---------- */

.pub { padding: 1rem 0; border-bottom: 1px solid var(--border); }
.pub:last-child { border-bottom: 0; }
.pub p { margin: 0 0 0.3rem; }
.pub__title { font-weight: 650; color: var(--text-strong); }
a.pub__title:hover { color: var(--link); }
.pub__authors { color: var(--text); font-size: 0.95rem; }
.pub__authors strong { font-weight: 700; }
.pub__links { font-size: 0.92rem; }
.pub__links a { font-weight: 600; }
.pub__links .sep { color: var(--muted); margin: 0 0.35rem; }
.pub ul { margin: 0.35rem 0 0; font-size: 0.95rem; }

.badge {
  display: inline-block; margin-right: 0.45rem; padding: 0.12em 0.55em;
  border-radius: 4px; background: var(--badge-bg); color: var(--badge-text);
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.02em;
  vertical-align: 0.12em; white-space: nowrap;
}
.badge--alt { background: var(--badge-alt-bg); color: var(--badge-alt-text); }
.badge--award { background: #b7791f; color: #fff; }
[data-theme="dark"] .badge--award { background: #5c4314; color: #f6dfa8; }

.note { color: var(--muted); font-size: 0.9rem; }

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

.footer {
  max-width: 1180px; margin: 0 auto; padding: 1.5rem 1.25rem 2.5rem;
  border-top: 1px solid var(--border); color: var(--muted); font-size: 0.85rem;
  display: flex; flex-wrap: wrap; justify-content: space-between; gap: 0.5rem;
}
.footer a { color: inherit; }

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

@media (max-width: 1040px) {
  .nav__list a { padding: 0.4rem 0.45rem; font-size: 0.9rem; }
  .nav__list a::after { left: 0.45rem; right: 0.45rem; }
}

@media (max-width: 920px) {
  .nav-toggle { display: inline-flex; }
  .nav { position: static; }
  .nav__list {
    display: none; position: absolute; top: var(--nav-h); left: 0; right: 0;
    flex-direction: column; gap: 0; padding: 0.4rem 1.25rem 0.8rem;
    background: var(--bg); border-bottom: 1px solid var(--border); box-shadow: var(--shadow);
  }
  .nav__list.is-open { display: flex; }
  .nav__list a { padding: 0.55rem 0; font-size: 1rem; }
  .nav__list a::after { display: none; }

  .layout { grid-template-columns: minmax(0, 1fr); gap: 1.5rem; padding-top: 1.5rem; }
  .sidebar {
    position: static; display: grid; grid-template-columns: 96px minmax(0, 1fr);
    column-gap: 1.1rem; align-items: center;
    padding-bottom: 1.25rem; border-bottom: 1px solid var(--border);
  }
  .profile__avatar { max-width: 96px; grid-row: span 2; }
  .profile__name { margin-top: 0; font-size: 1.3rem; }
  .profile__bio { margin-bottom: 0; font-size: 0.92rem; }
  .profile__links { display: none; }
  .profile__icons {
    grid-column: 1 / -1; display: flex; flex-wrap: wrap; gap: 0.25rem; margin-top: 0.9rem;
  }
  .profile__icons a {
    display: inline-flex; align-items: center; justify-content: center;
    width: 2.4rem; height: 2.4rem; border-radius: 8px; color: var(--muted); font-size: 1.15rem;
  }
  .profile__icons a:hover { color: var(--link); background: var(--surface); text-decoration: none; }
  .content > section:first-child > h1 { margin-top: 0.5rem; }
}

@media (max-width: 520px) {
  html { font-size: 15px; }
  .masthead__inner, .layout, .footer { padding-left: 1rem; padding-right: 1rem; }
  .nav__list { padding-left: 1rem; padding-right: 1rem; }
  .news li .date { min-width: 0; margin-right: 0.25rem; }
  .content h1 { font-size: 1.4rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}

@media print {
  .masthead, .profile__icons, .footer { display: none; }
  .layout { display: block; }
  .sidebar { position: static; }
}