/* ==========================================================================
   Bharat AI — Design System
   ========================================================================== */

:root {
  /* Brand */
  --ink:        #0B1220;
  --ink-2:      #111A2E;
  --ink-3:      #1A2440;
  --paper:      #FFFFFF;
  --paper-2:    #F7F9FC;
  --paper-3:    #EDF1F7;

  --saffron:    #E87722;
  --saffron-dk: #C25E12;
  --indigo:     #2F4BFF;
  --indigo-dk:  #1E33C7;
  --teal:       #0FA3A3;
  --green:      #16A34A;
  --red:        #DC2626;

  --text:       #101828;
  --text-2:     #475467;
  --text-3:     #77839A;
  --line:       #DFE5EE;
  --line-2:     #EAEEF4;

  /* Type */
  --sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono: "JetBrains Mono", "SF Mono", ui-monospace, Menlo, Consolas, monospace;

  /* Space */
  --r-sm: 6px;
  --r:    10px;
  --r-lg: 16px;
  --r-xl: 24px;

  --shadow-sm: 0 1px 2px rgba(16,24,40,.05);
  --shadow:    0 4px 16px rgba(16,24,40,.07);
  --shadow-lg: 0 18px 48px rgba(16,24,40,.12);

  --maxw: 1160px;
}

/* Reset ------------------------------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--sans);
  font-size: 16.5px;
  line-height: 1.65;
  color: var(--text);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
}
img, svg, canvas { max-width: 100%; display: block; }
a { color: var(--indigo); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.2; letter-spacing: -.02em; margin: 0 0 .5em; font-weight: 700; }
h1 { font-size: clamp(2.1rem, 4.6vw, 3.4rem); letter-spacing: -.035em; }
h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); letter-spacing: -.028em; }
h3 { font-size: 1.22rem; }
h4 { font-size: 1.02rem; }
p  { margin: 0 0 1.1em; }
code, pre, kbd { font-family: var(--mono); font-size: .88em; }
hr { border: 0; border-top: 1px solid var(--line); margin: 2.5rem 0; }

/* Layout ----------------------------------------------------------------- */
.wrap { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.wrap-narrow { max-width: 780px; }
.section { padding: 76px 0; }
.section-sm { padding: 48px 0; }
.section-tint { background: var(--paper-2); border-block: 1px solid var(--line-2); }
.center { text-align: center; }
.grid { display: grid; gap: 22px; }
.g2 { grid-template-columns: repeat(2, 1fr); }
.g3 { grid-template-columns: repeat(3, 1fr); }
.g4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 900px) { .g3, .g4 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 640px) { .g2, .g3, .g4 { grid-template-columns: 1fr; } }

/* Header ----------------------------------------------------------------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.88);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line-2);
}
.nav { display: flex; align-items: center; gap: 28px; height: 66px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; letter-spacing: -.03em;
         font-size: 1.12rem; color: var(--ink); text-decoration: none; }
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 30px; height: 30px; border-radius: 8px; flex: 0 0 30px;
  background: linear-gradient(135deg, var(--saffron), #E8A22C 55%, var(--indigo));
  display: grid; place-items: center; color: #fff; font-size: .78rem; font-weight: 800;
}
.brand small { display:block; font-size:.62rem; font-weight:600; letter-spacing:.13em;
               text-transform:uppercase; color: var(--text-3); margin-top:-3px; }
.nav-links { display: flex; gap: 24px; margin-left: auto; align-items: center; }
.nav-links a { color: var(--text-2); font-size: .93rem; font-weight: 500; }
.nav-links a:hover, .nav-links a[aria-current="page"] { color: var(--ink); text-decoration: none; }
.nav-toggle { display:none; background:none; border:1px solid var(--line); border-radius:8px;
              padding:7px 10px; margin-left:auto; cursor:pointer; font-size:1rem; }
@media (max-width: 820px) {
  .nav-toggle { display: block; }
  .nav-links {
    display: none; position: absolute; top: 66px; left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 0;
    background: #fff; border-bottom: 1px solid var(--line); padding: 8px 24px 16px;
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 11px 0; border-bottom: 1px solid var(--line-2); }
  .nav-links .btn { margin-top: 12px; text-align: center; border-bottom: 0; }
}

/* Buttons ---------------------------------------------------------------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 11px 20px; border-radius: var(--r); border: 1px solid transparent;
  font-size: .94rem; font-weight: 600; cursor: pointer; font-family: inherit;
  transition: transform .12s ease, box-shadow .18s ease, background .18s ease;
  text-decoration: none;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn-primary { background: var(--ink); color: #fff; box-shadow: var(--shadow-sm); }
.btn-primary:hover { background: var(--ink-3); box-shadow: var(--shadow); }
.btn-accent  { background: var(--saffron); color: #fff; }
.btn-accent:hover { background: var(--saffron-dk); }
.btn-ghost   { background: #fff; color: var(--ink); border-color: var(--line); }
.btn-ghost:hover { border-color: #C3CDDC; background: var(--paper-2); }
.btn-sm { padding: 7px 14px; font-size: .86rem; }

/* Badges / pills --------------------------------------------------------- */
.pill {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 5px 12px; border-radius: 999px; font-size: .76rem; font-weight: 600;
  letter-spacing: .02em; background: var(--paper-3); color: var(--text-2);
}
.pill-accent { background: rgba(232,119,34,.12); color: var(--saffron-dk); }
.pill-indigo { background: rgba(47,75,255,.10);  color: var(--indigo-dk); }
.pill-teal   { background: rgba(15,163,163,.12); color: #0B7C7C; }
.pill-green  { background: rgba(22,163,74,.12);  color: #12803A; }
.eyebrow { font-size: .78rem; font-weight: 700; letter-spacing: .14em; text-transform: uppercase;
           color: var(--saffron-dk); margin-bottom: 12px; }

/* Cards ------------------------------------------------------------------ */
.card {
  background: #fff; border: 1px solid var(--line); border-radius: var(--r-lg);
  padding: 26px; transition: border-color .18s, box-shadow .18s, transform .18s;
}
.card h3 { margin-bottom: .35em; }
.card p:last-child { margin-bottom: 0; }
a.card:hover { text-decoration: none; border-color: #C6D0E0; box-shadow: var(--shadow); transform: translateY(-2px); }
.card-icon {
  width: 40px; height: 40px; border-radius: 10px; display: grid; place-items: center;
  font-size: 1.1rem; margin-bottom: 16px; background: var(--paper-3);
}
.lead { font-size: 1.1rem; color: var(--text-2); }

/* Hero ------------------------------------------------------------------- */
.hero {
  background:
    radial-gradient(900px 420px at 12% -10%, rgba(232,119,34,.13), transparent 60%),
    radial-gradient(760px 420px at 88% 0%, rgba(47,75,255,.12), transparent 62%),
    var(--paper);
  border-bottom: 1px solid var(--line-2);
  padding: 84px 0 72px;
}
.hero h1 { max-width: 15ch; }
.hero .lead { max-width: 56ch; font-size: 1.18rem; }
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 30px; }
.hero-grid { display: grid; grid-template-columns: 1.1fr .9fr; gap: 48px; align-items: center; }
@media (max-width: 940px) { .hero-grid { grid-template-columns: 1fr; gap: 34px; } }

.stat-row { display: flex; gap: 40px; margin-top: 42px; flex-wrap: wrap; }
.stat b { display: block; font-size: 1.6rem; letter-spacing: -.03em; }
.stat span { font-size: .84rem; color: var(--text-3); }

/* Footer ----------------------------------------------------------------- */
.site-footer { background: var(--ink); color: #A9B4C7; padding: 56px 0 30px; margin-top: 0; }
.site-footer h4 { color: #fff; font-size: .82rem; letter-spacing: .12em; text-transform: uppercase; margin-bottom: 14px; }
.site-footer a { color: #A9B4C7; font-size: .92rem; display: block; padding: 5px 0; }
.site-footer a:hover { color: #fff; text-decoration: none; }
.site-footer .brand { color: #fff; }
.footer-bottom {
  border-top: 1px solid rgba(255,255,255,.10); margin-top: 38px; padding-top: 22px;
  display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; font-size: .85rem;
}

/* Lesson layout ---------------------------------------------------------- */
.lesson-shell { display: grid; grid-template-columns: 240px 1fr; gap: 52px; padding: 44px 0 80px; align-items: start; }
@media (max-width: 980px) { .lesson-shell { grid-template-columns: 1fr; gap: 26px; } }
.toc { position: sticky; top: 90px; font-size: .9rem; }
.toc strong { display:block; font-size:.74rem; letter-spacing:.12em; text-transform:uppercase;
              color: var(--text-3); margin-bottom: 12px; }
.toc a { display: block; padding: 6px 0 6px 13px; border-left: 2px solid var(--line);
         color: var(--text-2); }
.toc a:hover { color: var(--ink); border-left-color: var(--saffron); text-decoration: none; }
@media (max-width: 980px) { .toc { position: static; display: none; } }

.lesson-body { max-width: 740px; font-size: 1.04rem; }
.lesson-body h2 { margin-top: 2.2em; padding-top: .2em; }
.lesson-body h3 { margin-top: 1.8em; }
.lesson-body ul, .lesson-body ol { padding-left: 1.25em; margin: 0 0 1.2em; }
.lesson-body li { margin-bottom: .5em; }
.lesson-body strong { font-weight: 650; }
.lesson-meta { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-bottom: 18px; }

.callout {
  border-left: 3px solid var(--indigo); background: rgba(47,75,255,.045);
  padding: 16px 20px; border-radius: 0 var(--r) var(--r) 0; margin: 1.6em 0;
}
.callout.warn { border-left-color: var(--saffron); background: rgba(232,119,34,.06); }
.callout.key  { border-left-color: var(--teal);    background: rgba(15,163,163,.06); }
.callout p:last-child { margin-bottom: 0; }
.callout b { display: block; margin-bottom: 4px; font-size: .8rem; letter-spacing: .1em;
             text-transform: uppercase; color: var(--text-2); }

pre.code {
  background: var(--ink); color: #D9E2F1; padding: 18px 20px; border-radius: var(--r);
  overflow-x: auto; font-size: .84rem; line-height: 1.6; margin: 1.4em 0;
}
pre.code .c { color: #6F7F9B; }
pre.code .k { color: #F2A65A; }
pre.code .s { color: #7FD1AE; }
code.inline { background: var(--paper-3); padding: 2px 6px; border-radius: 5px; color: var(--ink-3); }

.formula {
  background: var(--paper-2); border: 1px solid var(--line-2); border-radius: var(--r);
  padding: 14px 18px; margin: 1.3em 0; font-family: var(--mono); font-size: .92rem;
  overflow-x: auto; text-align: center; color: var(--ink-3);
}

/* Interactive lab widget ------------------------------------------------- */
.lab {
  border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden;
  margin: 2em 0; background: #fff; box-shadow: var(--shadow-sm);
}
.lab-head {
  display: flex; align-items: center; gap: 10px; padding: 13px 18px;
  background: var(--paper-2); border-bottom: 1px solid var(--line-2);
}
.lab-head .dot { width: 8px; height: 8px; border-radius: 99px; background: var(--saffron); flex:0 0 8px; }
.lab-head b { font-size: .93rem; }
.lab-head .pill { margin-left: auto; }
.lab-body { padding: 20px 18px; }
.lab-note { font-size: .87rem; color: var(--text-2); margin: 14px 0 0; }

.ctrl { display: grid; grid-template-columns: 120px 1fr 68px; gap: 12px; align-items: center;
        margin-bottom: 12px; font-size: .88rem; }
.ctrl label { color: var(--text-2); font-weight: 500; }
.ctrl output { font-family: var(--mono); font-size: .85rem; text-align: right; color: var(--ink); }
@media (max-width: 520px) { .ctrl { grid-template-columns: 96px 1fr 58px; gap: 8px; font-size:.82rem; } }
input[type=range] { width: 100%; accent-color: var(--saffron); height: 22px; }
select, input[type=text], input[type=number], textarea {
  font-family: inherit; font-size: .92rem; padding: 8px 11px;
  border: 1px solid var(--line); border-radius: var(--r-sm); background: #fff; color: var(--text);
}
select:focus, input:focus, textarea:focus { outline: 2px solid rgba(47,75,255,.35); outline-offset: 1px; }

.readout { display: flex; gap: 22px; flex-wrap: wrap; margin-top: 14px;
           padding-top: 14px; border-top: 1px dashed var(--line); }
.readout div span { display: block; font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; color: var(--text-3); }
.readout div b { font-family: var(--mono); font-size: 1.02rem; }

.tokens { display: flex; flex-wrap: wrap; gap: 5px; margin-top: 6px; }
.tok { font-family: var(--mono); font-size: .82rem; padding: 3px 7px; border-radius: 5px;
       background: var(--paper-3); border: 1px solid var(--line); white-space: pre; }

/* Track / module list ---------------------------------------------------- */
.module {
  border: 1px solid var(--line); border-radius: var(--r-lg); margin-bottom: 16px;
  background: #fff; overflow: hidden;
}
.module-head { display: flex; gap: 16px; align-items: flex-start; padding: 22px 24px; }
.module-num {
  width: 34px; height: 34px; flex: 0 0 34px; border-radius: 9px; display: grid; place-items: center;
  background: var(--ink); color: #fff; font-weight: 700; font-size: .88rem;
}
.module-head h3 { margin-bottom: .25em; }
.module-head p { margin: 0; color: var(--text-2); font-size: .95rem; }
.module ul { margin: 0; padding: 0 24px 22px 74px; list-style: none; }
.module ul li {
  padding: 9px 0; border-top: 1px solid var(--line-2);
  display: flex; gap: 12px; align-items: center; font-size: .95rem;
}
.module ul li .pill { margin-left: auto; flex: 0 0 auto; }
@media (max-width: 560px) { .module ul { padding-left: 24px; } }

/* Prev/next -------------------------------------------------------------- */
.pager { display: flex; justify-content: space-between; gap: 14px; margin-top: 56px;
         padding-top: 26px; border-top: 1px solid var(--line); flex-wrap: wrap; }
.pager a { font-weight: 600; font-size: .95rem; }
.pager span { display: block; font-size: .74rem; letter-spacing: .1em; text-transform: uppercase; color: var(--text-3); }

/* Utility ---------------------------------------------------------------- */
.mt0 { margin-top: 0; } .mb0 { margin-bottom: 0; }
.muted { color: var(--text-2); }
.small { font-size: .88rem; }
canvas { border-radius: var(--r-sm); }
.free-banner {
  background: var(--ink); color: #DCE4F0; text-align: center; font-size: .84rem; padding: 8px 16px;
}
.free-banner b { color: #fff; }