/*
  Bilateral Binaural Blog
  Premium dark editorial — Playfair Display + Inter
  No animations. Clean structured layout.
*/
@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,400;0,500;1,400&family=Inter:wght@300;400;500;600&display=swap');

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}

:root{
  --bg:#0c0c0c;
  --bg1:#141414;
  --bg2:#1c1c1c;
  --border:rgba(255,255,255,0.09);
  --border2:rgba(255,255,255,0.17);
  --ink1:#efefef;
  --ink2:#9a9a9a;
  --ink3:#555;
  --accent:#4f8ef5;
  --accent-bg:rgba(79,142,245,0.08);
  --accent-line:rgba(79,142,245,0.28);
  --serif:'Playfair Display',Georgia,serif;
  --sans:'Inter',system-ui,sans-serif;
  --col:660px;
  --page:1080px;
}

html{background:var(--bg);color:var(--ink1);font-family:var(--sans);font-size:16px;-webkit-font-smoothing:antialiased}
body{min-height:100vh}

/* NAV */
.nav{position:sticky;top:0;z-index:200;height:56px;border-bottom:1px solid var(--border);background:rgba(12,12,12,0.94);backdrop-filter:blur(16px);display:flex;align-items:center}
.nav-inner{max-width:var(--page);width:100%;margin:0 auto;padding:0 32px;display:flex;align-items:center}
.nav-logo{font-size:11px;font-weight:500;letter-spacing:.1em;text-transform:uppercase;color:var(--ink3);text-decoration:none;transition:color .15s}
.nav-logo:hover{color:var(--ink1)}
.nav-sep{flex:1}
.nav-link{font-size:12px;color:var(--ink3);text-decoration:none;margin-left:28px;transition:color .15s;letter-spacing:.02em}
.nav-link:hover,.nav-link.active{color:var(--ink2)}

/* BACK */
.back-link{max-width:var(--page);margin:0 auto;padding:24px 32px 0}
.back-link a{font-size:12px;color:var(--ink3);text-decoration:none;letter-spacing:.03em;display:inline-flex;align-items:center;gap:6px;transition:color .15s}
.back-link a:hover{color:var(--ink1)}

/* INDEX HEADER */
.index-header{max-width:var(--page);margin:0 auto;padding:72px 32px 56px;border-bottom:1px solid var(--border)}
.index-eyebrow{font-size:10px;font-weight:600;letter-spacing:.14em;text-transform:uppercase;color:var(--accent);margin-bottom:20px}
.index-header h1{font-family:var(--serif);font-weight:400;font-size:clamp(36px,5vw,56px);line-height:1.08;letter-spacing:-.02em;color:var(--ink1);margin-bottom:20px}
.index-header p{font-size:15px;color:var(--ink2);font-weight:300;max-width:420px;line-height:1.75}

/* POST GRID */
.post-grid{max-width:var(--page);margin:0 auto;padding:0 32px 96px;display:grid;grid-template-columns:repeat(3,1fr)}
.post-card{padding:32px 32px 32px 0;text-decoration:none;display:flex;flex-direction:column;gap:12px;border-bottom:1px solid var(--border);border-right:1px solid var(--border);border-top:2px solid transparent;transition:border-top-color .2s}
.post-card:nth-child(3n){border-right:none;padding-right:0}
.post-card:hover{border-top-color:var(--accent)}
.post-card:hover .post-title{color:var(--ink1)}
.post-eyebrow{font-size:10px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.post-title{font-family:var(--serif);font-size:18px;font-weight:400;line-height:1.35;color:var(--ink2);transition:color .15s}
.post-excerpt{font-size:13px;color:var(--ink3);line-height:1.7;font-weight:300;flex:1}
.post-meta{display:flex;align-items:center;gap:8px;font-size:11px;color:var(--ink3);margin-top:4px;letter-spacing:.03em;border-top:1px solid var(--border);padding-top:14px}
.dot{width:2px;height:2px;border-radius:50%;background:var(--ink3)}

/* ARTICLE LAYOUT */
.article-outer{max-width:var(--page);margin:0 auto;padding:0 32px;display:grid;grid-template-columns:1fr 220px;gap:72px;align-items:start}
.article-main{min-width:0}

/* SIDEBAR */
.article-sidebar{position:sticky;top:80px;padding-top:56px}
.sidebar-label{font-size:10px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--ink3);margin-bottom:16px}
.toc{list-style:none}
.toc li a{display:block;font-size:12px;color:var(--ink3);text-decoration:none;padding:7px 0 7px 14px;border-left:1px solid var(--border);line-height:1.4;transition:color .15s,border-color .15s}
.toc li a:hover{color:var(--ink1);border-left-color:var(--accent)}
.sidebar-cta{margin-top:36px;padding:18px;background:var(--bg1);border:1px solid var(--border)}
.sidebar-cta p{font-size:11px;color:var(--ink3);line-height:1.65;margin-bottom:14px}
.sidebar-cta-btn{display:block;text-align:center;font-size:10px;font-weight:600;letter-spacing:.1em;text-transform:uppercase;color:var(--accent);text-decoration:none;padding:9px 12px;border:1px solid var(--accent-line);background:var(--accent-bg);transition:background .15s,border-color .15s}
.sidebar-cta-btn:hover{background:rgba(79,142,245,.14);border-color:var(--accent)}

/* ARTICLE HEADER */
.article-header{padding:56px 0 40px;border-bottom:1px solid var(--border);margin-bottom:48px}
.article-eyebrow{display:flex;align-items:center;gap:12px;margin-bottom:20px}
.article-tag{font-size:10px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.eyebrow-sep{width:1px;height:10px;background:var(--border2)}
.article-date{font-size:11px;color:var(--ink3);letter-spacing:.04em}
.article-header h1{font-family:var(--serif);font-weight:400;font-size:clamp(28px,4vw,44px);line-height:1.12;letter-spacing:-.02em;color:var(--ink1);margin-bottom:24px}
.article-lede{font-size:17px;color:var(--ink2);font-weight:300;line-height:1.75;max-width:540px;margin-bottom:24px}
.article-meta-bar{display:flex;align-items:center;gap:12px;font-size:11px;color:var(--ink3);letter-spacing:.04em}
.meta-sep{width:2px;height:2px;border-radius:50%;background:var(--border2)}

/* HERO VISUAL */
.article-hero-visual{margin-bottom:48px;border:1px solid var(--border);background:var(--bg1);overflow:hidden}
.article-hero-visual svg{display:block;width:100%;height:auto}

/* BODY PROSE */
.article-body{font-size:16px;line-height:1.85;color:var(--ink2);font-weight:300}
.article-body p{margin-bottom:24px}
.article-body h2{font-family:var(--serif);font-weight:400;font-size:24px;line-height:1.2;letter-spacing:-.01em;color:var(--ink1);margin:56px 0 20px;padding-top:56px;border-top:1px solid var(--border)}
.article-body h2:first-child{margin-top:0;padding-top:0;border-top:none}
.article-body h3{font-size:14px;font-weight:600;letter-spacing:.02em;color:var(--ink1);margin:32px 0 12px}
.article-body ul,.article-body ol{padding-left:20px;margin-bottom:24px}
.article-body li{margin-bottom:8px;line-height:1.75;color:var(--ink2)}
.article-body strong{font-weight:600;color:var(--ink1)}
.article-body em{font-style:italic;color:var(--ink1)}
.article-body a{color:var(--ink1);text-decoration:underline;text-decoration-color:var(--border2);text-underline-offset:3px;transition:text-decoration-color .15s}
.article-body a:hover{text-decoration-color:var(--accent)}

/* CALLOUT */
.callout{margin:32px 0;padding:18px 20px;background:var(--bg1);border:1px solid var(--border);border-left:2px solid var(--accent)}
.callout p{font-size:14px!important;color:var(--ink2)!important;margin-bottom:0!important;line-height:1.7}
.callout-warn{border-left-color:#c97a38}

/* PULL QUOTE */
.pull-quote{margin:40px 0;padding:32px 0;border-top:1px solid var(--border);border-bottom:1px solid var(--border)}
.pull-quote p{font-family:var(--serif)!important;font-style:italic;font-size:22px!important;line-height:1.5!important;color:var(--ink1)!important;margin:0 auto!important;max-width:500px;text-align:center;font-weight:400!important}

/* KEY CONCEPT */
.key-concept{margin:32px 0;padding:20px;background:var(--bg1);border:1px solid var(--border);border-top:2px solid var(--border2)}
.key-concept-label{font-size:10px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--ink3);margin-bottom:10px;display:block}
.key-concept p{font-size:14px!important;color:var(--ink2)!important;margin-bottom:0!important;line-height:1.7}

/* STAT GRID */
.stat-grid{display:grid;grid-template-columns:repeat(4,1fr);border:1px solid var(--border);margin:32px 0}
.stat-card{padding:24px 20px;text-align:center;border-right:1px solid var(--border)}
.stat-card:last-child{border-right:none}
.stat-number{font-family:var(--serif);font-size:30px;font-weight:400;color:var(--ink1);line-height:1;margin-bottom:8px}
.stat-label{font-size:10px;font-weight:500;letter-spacing:.1em;text-transform:uppercase;color:var(--ink3);line-height:1.4}

/* COMPARISON TABLE */
.comparison-table{width:100%;border-collapse:collapse;margin:32px 0;font-size:14px;border:1px solid var(--border)}
.comparison-table thead tr{background:var(--bg1)}
.comparison-table th{padding:12px 16px;text-align:left;font-size:10px;font-weight:600;letter-spacing:.1em;text-transform:uppercase;color:var(--ink3);border-bottom:1px solid var(--border2)}
.comparison-table td{padding:12px 16px;border-bottom:1px solid var(--border);color:var(--ink2);font-weight:300;line-height:1.5;vertical-align:top}
.comparison-table tr:last-child td{border-bottom:none}
.comparison-table tbody tr:hover td{background:var(--bg1)}
.col-highlight{color:var(--ink1)!important;font-weight:500!important}

/* TWO COL */
.two-col{display:grid;grid-template-columns:1fr 1fr;border:1px solid var(--border);margin:32px 0}
.two-col-item{padding:24px;border-right:1px solid var(--border)}
.two-col-item:last-child{border-right:none}
.two-col-item h4{font-size:10px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--ink3);margin-bottom:10px}
.two-col-item p{font-size:13px!important;color:var(--ink2)!important;margin-bottom:0!important;line-height:1.7;font-weight:300}

/* STEP LIST */
.step-list{list-style:none!important;padding-left:0!important;margin:32px 0!important;border:1px solid var(--border)}
.step-list li{display:flex!important;gap:16px;align-items:flex-start;padding:20px!important;border-bottom:1px solid var(--border);background:var(--bg1);margin-bottom:0!important;transition:background .15s}
.step-list li:last-child{border-bottom:none}
.step-list li:hover{background:var(--bg2)}
.step-num{flex-shrink:0;width:26px;height:26px;border-radius:50%;border:1px solid var(--border2);color:var(--accent);font-size:11px;font-weight:600;display:flex;align-items:center;justify-content:center;margin-top:1px}
.step-content{flex:1}
.step-content strong{display:block;font-size:14px;font-weight:600;color:var(--ink1)!important;margin-bottom:4px}
.step-content span{font-size:13px;color:var(--ink3);line-height:1.65;font-weight:300}

/* FREQ BANDS */
.freq-bands{margin:32px 0;padding:24px;background:var(--bg1);border:1px solid var(--border);display:flex;flex-direction:column;gap:14px}
.freq-band{display:flex;align-items:center;gap:14px}
.freq-label{font-size:12px;font-weight:500;color:var(--ink1);width:80px;flex-shrink:0}
.freq-bar-wrap{flex:1;height:4px;background:rgba(255,255,255,0.05)}
.freq-bar{height:100%}
.freq-desc{font-size:11px;color:var(--ink3);width:160px;flex-shrink:0}

/* TIP LIST */
.tip-list{list-style:none!important;padding-left:0!important;margin:24px 0!important}
.tip-list li{font-size:14px!important;padding:12px 16px 12px 20px!important;margin-bottom:4px!important;border-left:2px solid var(--border);color:var(--ink2)!important;line-height:1.65!important;transition:border-color .15s}
.tip-list li:hover{border-left-color:var(--accent)}

/* CTA */
.article-cta{margin-top:64px;padding-top:40px;border-top:1px solid var(--border)}
.cta-box{padding:36px;background:var(--bg1);border:1px solid var(--border);display:flex;align-items:center;justify-content:space-between;gap:32px}
.cta-box-text h3{font-family:var(--serif);font-size:22px;font-weight:400;color:var(--ink1);margin-bottom:6px;letter-spacing:-.01em}
.cta-box-text p{font-size:13px;color:var(--ink3);font-weight:300;line-height:1.65;max-width:320px}
.cta-btn{flex-shrink:0;display:inline-block;white-space:nowrap;padding:11px 28px;background:var(--accent-bg);border:1px solid var(--accent-line);color:var(--accent);font-size:11px;font-weight:600;letter-spacing:.1em;text-transform:uppercase;text-decoration:none!important;transition:background .15s,border-color .15s,color .15s}
.cta-btn:hover{background:var(--accent);border-color:var(--accent);color:#000}

/* FOOTER */
.footer{border-top:1px solid var(--border);padding:28px 32px;text-align:center}
.footer p{font-size:11px;color:var(--ink3);letter-spacing:.04em}
.footer a{color:inherit;text-decoration:none}
.footer a:hover{color:var(--ink2)}

/* RESPONSIVE */
@media(max-width:1024px){
  .article-outer{grid-template-columns:1fr;gap:0}
  .article-sidebar{display:none}
  .post-grid{grid-template-columns:repeat(2,1fr)}
  .post-card:nth-child(3n){border-right:1px solid var(--border)}
  .post-card:nth-child(2n){border-right:none}
}
@media(max-width:640px){
  .post-grid{grid-template-columns:1fr;padding:0 20px 64px}
  .post-card{border-right:none!important;padding:28px 0}
  .index-header{padding:48px 20px 40px}
  .article-outer{padding:0 20px}
  .article-header{padding:40px 0 32px}
  .stat-grid{grid-template-columns:repeat(2,1fr)}
  .stat-card:nth-child(2){border-right:none}
  .stat-card:nth-child(n+3){border-top:1px solid var(--border)}
  .two-col{grid-template-columns:1fr}
  .two-col-item{border-right:none;border-bottom:1px solid var(--border)}
  .two-col-item:last-child{border-bottom:none}
  .freq-desc{display:none}
  .cta-box{flex-direction:column;align-items:flex-start;gap:20px}
  .back-link{padding:20px 20px 0}
  .nav-inner{padding:0 20px}
  .footer{padding:24px 20px}
}