:root{
  --bg:#000000;
  --bg-elevated:#0A0A0A;
  --border:#1E1E1E;
  --border-strong:#333333;
  --text:#FFFFFF;
  --text-dim:#8F8F8F;
  --text-faint:#565656;
  --good:#8FD19E;
}
*{box-sizing:border-box;}
html,body{margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  background:var(--bg);
  color:var(--text);
  font-family:'Inter', sans-serif;
  min-height:100vh;
  -webkit-font-smoothing:antialiased;
  position:relative;
}
/* Sutil grão de ruído sobre o fundo preto — quebra a chapada sem tirar o minimalismo */
body::before{
  content:"";
  position:fixed;
  inset:0;
  pointer-events:none;
  opacity:0.035;
  z-index:0;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}
body > *{position:relative; z-index:1;}
a{color:inherit; text-decoration:none;}
.wrap{max-width:980px;margin:0 auto;padding:0 28px;}
h1,h2,h3{font-family:'Space Grotesk', sans-serif;}

/* ---------- Scroll reveal ---------- */
.reveal{opacity:0; transform:translateY(14px); transition:opacity 0.7s ease, transform 0.7s ease;}
.reveal.visible{opacity:1; transform:translateY(0);}

/* ---------- Nav ---------- */
.site-nav{
  border-bottom:1px solid var(--border);
  padding:20px 0;
  position:sticky;
  top:0;
  z-index:10;
  background:rgba(0,0,0,0.72);
  backdrop-filter:blur(10px);
  -webkit-backdrop-filter:blur(10px);
  transition:box-shadow 0.3s ease, border-color 0.3s ease;
}
.site-nav.scrolled{
  box-shadow:0 8px 24px -12px rgba(0,0,0,0.8);
  border-color:var(--border-strong);
}
.site-nav .wrap{
  display:flex;
  align-items:center;
  justify-content:space-between;
  flex-wrap:wrap;
  gap:12px;
}
.logo{
  font-family:'Space Grotesk', sans-serif;
  font-size:15px;
  font-weight:700;
  letter-spacing:0.01em;
}
.nav-links{
  display:flex;
  gap:26px;
  font-size:13px;
  color:var(--text-dim);
}
.nav-links a:hover, .nav-links a.active{color:var(--text);}

/* ---------- Hero / sections ---------- */
.section{padding:64px 0;}
.section.tight{padding:38px 0;}
.section-head{
  text-align:center;
  max-width:60ch;
  margin:0 auto 36px;
}
.eyebrow{
  font-family:'IBM Plex Mono', monospace;
  font-size:11px;
  color:var(--text-faint);
  text-transform:uppercase;
  letter-spacing:0.08em;
  margin:0 0 16px;
}
h1{font-size:clamp(30px, 5vw, 40px);font-weight:700;line-height:1.15;letter-spacing:-0.01em;margin:0 0 18px;}
h1.hero-xl{font-size:clamp(36px, 6.5vw, 56px);}
h2{font-size:clamp(19px, 2.6vw, 22px);font-weight:700;line-height:1.35;margin:0 0 10px;}
.lede{font-size:16px;color:var(--text-dim);line-height:1.65;margin:0;}
.center{text-align:center;}

/* ---------- Symbol ---------- */
.symbol{
  display:flex;
  justify-content:center;
  padding:8px 0 54px;
}
.symbol .ring{
  width:110px;height:110px;
  border-radius:50%;
  border:1px solid var(--border-strong);
  display:flex;align-items:center;justify-content:center;
  animation:ring-pulse 5s ease-in-out infinite;
}
.symbol .core{
  width:52px;height:52px;
  border-radius:50%;
  border:1px solid var(--text-faint);
  box-shadow:0 0 0 0 rgba(255,255,255,0.08);
  animation:core-pulse 5s ease-in-out infinite;
}
@keyframes ring-pulse{
  0%,100%{transform:scale(1); border-color:var(--border-strong);}
  50%{transform:scale(1.06); border-color:#4a4a4a;}
}
@keyframes core-pulse{
  0%,100%{box-shadow:0 0 0 0 rgba(255,255,255,0.06);}
  50%{box-shadow:0 0 24px 6px rgba(255,255,255,0.06);}
}
@media (prefers-reduced-motion: reduce){
  .symbol .ring, .symbol .core{animation:none;}
}

/* ---------- Cards ---------- */
.card-grid{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(230px,1fr));
  gap:14px;
}
.card{
  background:var(--bg-elevated);
  border:1px solid var(--border);
  border-radius:2px;
  padding:24px 26px;
  transition:border-color 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}
.card:hover{
  border-color:var(--border-strong);
  transform:translateY(-3px);
  box-shadow:0 14px 30px -18px rgba(0,0,0,0.9);
}
.card.featured{border-color:var(--border-strong); border-width:1px;}
.card .num{
  font-family:'IBM Plex Mono', monospace;
  font-size:11px;
  color:var(--text-faint);
  display:block;margin-bottom:14px;
}
.card h3{font-size:15px; font-weight:700; margin:0 0 8px;}
.card p{font-size:13px; color:var(--text-dim); line-height:1.6; margin:0 0 14px;}
.card .go{font-size:12.5px; color:var(--text); font-weight:500; border-bottom:1px solid var(--border-strong); padding-bottom:2px;}

/* ---------- Badges ---------- */
.badge{
  display:inline-block;
  font-family:'IBM Plex Mono', monospace;
  font-size:10.5px;
  text-transform:uppercase;
  letter-spacing:0.06em;
  color:var(--text);
  border:1px solid var(--border-strong);
  padding:4px 10px;
  border-radius:2px;
  margin-bottom:12px;
}

/* ---------- Buttons ---------- */
.btn{
  display:inline-block;
  background:var(--text);
  color:#000;
  font-weight:600;
  font-size:13.5px;
  padding:13px 26px;
  border-radius:2px;
  border:1px solid var(--text);
  cursor:pointer;
  transition:background 0.2s ease, transform 0.2s ease;
}
.btn:hover{background:#e6e6e6; transform:translateY(-1px);}
.btn.ghost{
  background:none;
  border:1px solid var(--border-strong);
  color:var(--text);
  transition:border-color 0.2s ease, transform 0.2s ease;
}
.btn.ghost:hover{border-color:var(--text); transform:translateY(-1px);}
.btn.block{width:100%; text-align:center;}

/* ---------- Chat preview ---------- */
.chat-preview{
  background:var(--bg-elevated);
  border:1px solid var(--border);
  border-radius:2px;
  padding:20px 22px;
  max-width:520px;
  margin:0 auto;
}
.chat-preview .label{
  font-family:'IBM Plex Mono', monospace;
  font-size:10.5px;
  color:var(--text-faint);
  text-transform:uppercase;
  letter-spacing:0.06em;
  margin:0 0 14px;
  display:flex;align-items:center;gap:8px;
}
.chat-preview .label .dot{width:6px;height:6px;border-radius:50%;background:var(--good);}
.bubble-row{display:flex; flex-direction:column; gap:9px; margin-bottom:6px;}
.bubble{
  font-size:13.5px;
  line-height:1.55;
  padding:10px 14px;
  border-radius:2px;
  max-width:86%;
}
.bubble.tutor{align-self:flex-start; background:#141414; border:1px solid var(--border);}
.bubble.user{align-self:flex-end; background:#fff; color:#000;}

/* ---------- Forms ---------- */
label{font-size:12.5px; color:var(--text-dim); display:block; margin-bottom:6px;}
input[type=text], input[type=email], select, textarea{
  width:100%;
  background:var(--bg-elevated);
  border:1px solid var(--border-strong);
  color:var(--text);
  font-family:'Inter', sans-serif;
  font-size:13.5px;
  padding:11px 13px;
  border-radius:2px;
}
textarea{resize:vertical; min-height:90px;}
input:focus, select:focus, textarea:focus{outline:1px solid var(--text); outline-offset:0;}
.field{margin-bottom:14px;}

/* ---------- Misc ---------- */
.muted-note{font-size:12px; color:var(--text-faint); line-height:1.6; text-align:center; max-width:54ch; margin:20px auto 0;}

.site-footer{
  border-top:1px solid var(--border);
  padding:28px 0;
  font-size:12px;
  color:var(--text-faint);
  text-align:center;
}