/* ═══════════════════════════════════════════════════════════
   NormalHeartRate.org — Bio-Neural Design System
   Used across all pages: index, about, privacy, blog/*
   ═══════════════════════════════════════════════════════════ */

/* TOKENS ─── */
:root{
  --bg:          #07080b;
  --bg-2:        #0c0e13;
  --bg-3:        #11141b;
  --surface:     rgba(255,255,255,0.025);
  --surface-2:   rgba(255,255,255,0.05);
  --line:        rgba(255,255,255,0.06);
  --line-2:      rgba(255,255,255,0.1);
  --text:        #e8eaee;
  --text-2:      #a8acb6;
  --text-3:      #6b6f7a;
  --text-4:      #44474f;
  --primary:     #ff2e51;
  --primary-2:   #ff5a78;
  --primary-rgb: 255,46,81;
  --accent:      #00e5ff;
  --accent-2:    #7af0ff;
  --accent-rgb:  0,229,255;
  --violet:      #b388ff;
  --green:       #2dd4bf;
  --amber:       #fbbf24;
  --orange:      #fb923c;
  --grid:        rgba(255,46,81,0.05);
  --glow:        0 0 28px rgba(255,46,81,0.25);
  --glow-soft:   0 0 60px rgba(255,46,81,0.12);
  --card-r:      18px;
  --card-r-lg:   24px;
}
[data-theme="light"]{
  --bg:          #f5f4f1;
  --bg-2:        #ffffff;
  --bg-3:        #ebe9e3;
  --surface:     rgba(10,10,15,0.025);
  --surface-2:   rgba(10,10,15,0.05);
  --line:        rgba(10,10,15,0.08);
  --line-2:      rgba(10,10,15,0.14);
  --text:        #0d0e12;
  --text-2:      #4a4d57;
  --text-3:      #74777f;
  --text-4:      #a9abb1;
  --primary:     #e11d48;
  --primary-2:   #f43f5e;
  --accent:      #0891b2;
  --accent-2:    #0e7490;
  --grid:        rgba(225,29,72,0.04);
  --glow:        0 0 24px rgba(225,29,72,0.18);
  --glow-soft:   0 0 60px rgba(225,29,72,0.08);
}

/* RESET / BASE ─── */
*{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  font-family:'Space Grotesk',ui-sans-serif,system-ui,sans-serif;
  background:var(--bg);
  color:var(--text);
  min-height:100vh;
  overflow-x:hidden;
  -webkit-font-smoothing:antialiased;
  font-feature-settings:"ss01","ss02","cv11";
  letter-spacing:-0.005em;
  line-height:1.6;
}

/* Subtle grid + radial background */
body::before{
  content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
  background:
    linear-gradient(to right, var(--grid) 1px, transparent 1px) 0 0/64px 64px,
    linear-gradient(to bottom, var(--grid) 1px, transparent 1px) 0 0/64px 64px,
    radial-gradient(circle at 50% 0%, rgba(var(--primary-rgb),0.12), transparent 50%),
    radial-gradient(circle at 80% 100%, rgba(var(--accent-rgb),0.05), transparent 40%);
  mask-image:radial-gradient(ellipse at center, black 30%, transparent 80%);
}
body::after{
  content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
  background:url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2'/%3E%3CfeColorMatrix values='0 0 0 0 1, 0 0 0 0 0.2, 0 0 0 0 0.3, 0 0 0 0.6 0'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  opacity:0.025;mix-blend-mode:overlay;
}

.content{position:relative;z-index:2;}

/* NAV ─── */
nav{
  display:flex;align-items:center;justify-content:space-between;
  padding:18px 32px;
  border-bottom:1px solid var(--line);
  background:rgba(7,8,11,0.7);backdrop-filter:blur(20px);
  position:sticky;top:0;z-index:100;
}
[data-theme="light"] nav{background:rgba(245,244,241,0.8);}
.nav-brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--text);}
.nav-brand svg{filter:drop-shadow(0 0 12px rgba(var(--primary-rgb),0.6));}
.nav-brand-text{font-size:1.05rem;font-weight:600;letter-spacing:-0.02em;}
.nav-brand-text span{color:var(--primary);}
.nav-right{display:flex;align-items:center;gap:8px;}
.nav-link{color:var(--text-2);text-decoration:none;font-size:0.86rem;font-weight:500;padding:6px 12px;border-radius:8px;transition:all 0.15s;}
.nav-link:hover{color:var(--text);background:var(--surface);}
.nav-link.active{color:var(--primary);}
.nav-cta{
  display:inline-flex;align-items:center;gap:8px;
  background:linear-gradient(135deg, var(--primary), var(--primary-2));
  color:#fff;text-decoration:none;
  padding:7px 14px;border-radius:8px;font-size:0.82rem;font-weight:500;
  box-shadow:0 6px 18px rgba(var(--primary-rgb),0.28);
  transition:all 0.2s;
}
.nav-cta:hover{transform:translateY(-1px);box-shadow:0 10px 24px rgba(var(--primary-rgb),0.4);}
.nav-icon-btn{
  display:inline-flex;align-items:center;justify-content:center;
  width:36px;height:36px;border-radius:10px;
  background:var(--surface);border:1px solid var(--line);
  color:var(--text-2);cursor:pointer;transition:all 0.15s;
  font-family:inherit;
}
.nav-icon-btn:hover{color:var(--primary);border-color:rgba(var(--primary-rgb),0.4);box-shadow:0 0 16px rgba(var(--primary-rgb),0.2);}

/* TYPOGRAPHY ─── */
h1,h2,h3,h4{color:var(--text);font-weight:600;letter-spacing:-0.025em;}
p{color:var(--text-2);}
a{color:var(--primary-2);}
strong{color:var(--text);font-weight:500;}

/* PAGE HEADER (for sub-pages) ─── */
.page-header{
  max-width:880px;margin:0 auto;padding:80px 32px 32px;
}
.page-eyebrow{
  display:inline-flex;align-items:center;gap:10px;
  font-family:'JetBrains Mono',monospace;
  font-size:0.7rem;letter-spacing:0.18em;text-transform:uppercase;
  color:var(--primary);margin-bottom:18px;
}
.page-eyebrow::before{content:'';width:24px;height:1px;background:var(--primary);}

.page-title{
  font-size:clamp(2rem, 5vw, 3.4rem);
  font-weight:600;line-height:1.05;letter-spacing:-0.035em;
  margin-bottom:14px;
}
.page-title em{
  font-style:italic;font-weight:500;
  background:linear-gradient(135deg, var(--primary), var(--primary-2));
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;
}
.page-sub{font-size:1.05rem;color:var(--text-2);line-height:1.7;max-width:660px;}

/* CONTAINER ─── */
.container{max-width:880px;margin:0 auto;padding:0 32px;}

/* SUBSECTION TITLE ─── */
.subsec-title{
  font-family:'JetBrains Mono',monospace;font-size:0.7rem;font-weight:500;letter-spacing:0.16em;text-transform:uppercase;
  color:var(--text-3);margin:28px 0 14px;
  display:flex;align-items:center;gap:14px;
}
.subsec-title::before{content:'';flex:0 0 8px;height:8px;background:var(--primary);border-radius:2px;box-shadow:0 0 12px var(--primary);}
.subsec-title::after{content:'';flex:1;height:1px;background:var(--line);}

/* CARDS ─── */
.card{
  background:var(--surface);border:1px solid var(--line);
  border-radius:var(--card-r);padding:24px;
}
.card-eyebrow{
  font-family:'JetBrains Mono',monospace;
  font-size:0.66rem;letter-spacing:0.14em;text-transform:uppercase;
  color:var(--text-3);margin-bottom:10px;
}

/* CTA BUTTON ─── */
.btn{
  display:inline-flex;align-items:center;gap:10px;
  padding:14px 28px;border-radius:14px;
  background:linear-gradient(135deg, var(--primary), var(--primary-2));
  color:#fff;text-decoration:none;
  font-family:inherit;font-size:0.92rem;font-weight:500;
  border:none;cursor:pointer;
  box-shadow:0 12px 32px rgba(var(--primary-rgb),0.32), inset 0 1px 0 rgba(255,255,255,0.25);
  transition:all 0.2s;
}
.btn:hover{transform:translateY(-2px);box-shadow:0 18px 40px rgba(var(--primary-rgb),0.42);}
.btn-ghost{
  background:transparent;color:var(--text);
  border:1px solid var(--line-2);
  box-shadow:none;
}
.btn-ghost:hover{border-color:var(--primary);color:var(--primary);background:rgba(var(--primary-rgb),0.05);box-shadow:0 0 18px rgba(var(--primary-rgb),0.12);}

/* TOOL CTA banner (used in articles + about) ─── */
.tool-cta{
  background:linear-gradient(135deg, rgba(var(--primary-rgb),0.12) 0%, rgba(var(--accent-rgb),0.04) 100%);
  border:1px solid rgba(var(--primary-rgb),0.25);
  border-radius:var(--card-r-lg);
  padding:36px 32px;text-align:center;margin:48px 0;
  position:relative;overflow:hidden;
}
.tool-cta::before{
  content:'';position:absolute;top:-50%;right:-20%;width:60%;height:200%;
  background:radial-gradient(ellipse at center, rgba(var(--primary-rgb),0.15) 0%, transparent 50%);
  pointer-events:none;
}
.tool-cta > *{position:relative;z-index:1;}
.tool-cta h3{font-size:1.3rem;font-weight:500;letter-spacing:-0.02em;margin-bottom:8px;}
.tool-cta p{font-size:0.92rem;color:var(--text-2);max-width:480px;margin:0 auto 22px;line-height:1.7;}

/* REFERENCES ─── */
.refs-card{
  background:var(--surface);border:1px solid var(--line);
  border-radius:var(--card-r);padding:24px;
}
.refs-title{
  font-family:'JetBrains Mono',monospace;font-size:0.7rem;letter-spacing:0.16em;text-transform:uppercase;
  color:var(--text-3);margin-bottom:16px;
}
.ref-item{
  display:flex;gap:12px;padding:10px 0;border-bottom:1px solid var(--line);
  font-size:0.78rem;color:var(--text-3);line-height:1.6;
}
.ref-item:last-child{border-bottom:none;padding-bottom:0;}
.ref-num{font-family:'JetBrains Mono',monospace;color:var(--primary);font-size:0.7rem;min-width:18px;margin-top:2px;font-weight:500;}
.ref-item a{color:var(--text-2);text-decoration:none;}
.ref-item a:hover{color:var(--primary);}

/* FOOTER ─── */
footer{
  text-align:center;padding:32px 24px;
  border-top:1px solid var(--line);
  font-family:'JetBrains Mono',monospace;font-size:0.74rem;
  color:var(--text-4);line-height:2;letter-spacing:0.02em;
}
footer a{color:var(--text-3);text-decoration:none;}
footer a:hover{color:var(--primary);}

/* MOBILE ─── */
@media(max-width:600px){
  nav{padding:14px 16px;}
  .nav-link.collapsible{display:none;}
  .page-header{padding:48px 16px 24px;}
  .container{padding:0 16px;}
  .tool-cta{padding:24px 18px;}
}