/* =============================================
   reinocheong.com — Design System v1.0
   Based on PRD: Minimal · Calm · Elegant · Editorial
   ============================================= */

/* ---------- Reset ---------- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}

/* ---------- Variables ---------- */
:root{
  --bg:#fff;
  --bg-secondary:#fafafa;
  --text:#111;
  --text-secondary:#666;
  --text-tertiary:#999;
  --border:#eaeaea;
  --accent:#1e3a5f;
  --accent-light:#2a5298;
  --accent-soft:rgba(30,58,95,.05);
  --reading-width:720px;
  --max-width:1120px;
  --nav-height:64px;
  --font-sans:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
  --font-serif:'IBM Plex Serif',Georgia,serif;
  --ease:cubic-bezier(.16,1,.3,1);
  --radius:6px;
}

/* ---------- Base ---------- */
body{
  font-family:var(--font-sans);
  font-size:16px;
  line-height:1.6;
  color:var(--text);
  background:var(--bg);
}
::selection{background:var(--accent);color:#fff}
a{color:var(--accent);text-decoration:none;transition:all .2s}
a:hover{opacity:.7}
img{max-width:100%;height:auto;display:block}

/* ---------- Container ---------- */
.container{max-width:var(--max-width);margin:0 auto;padding:0 40px}

/* ---------- Typography ---------- */
h1,h2,h3,h4{font-weight:500;line-height:1.2;letter-spacing:-.02em;color:var(--text)}
p{color:var(--text-secondary);line-height:1.7}
.serif{font-family:var(--font-serif)}

/* ---------- Nav ---------- */
nav{
  position:sticky;top:0;z-index:100;
  background:rgba(255,255,255,.92);
  backdrop-filter:blur(12px);
  -webkit-backdrop-filter:blur(12px);
  border-bottom:1px solid var(--border);
  height:var(--nav-height);
}
.nav-inner{
  max-width:var(--max-width);margin:0 auto;padding:0 40px;
  display:flex;align-items:center;justify-content:space-between;
  height:100%;
}
.nav-logo{
  font-size:1.05rem;font-weight:600;color:var(--text);
  letter-spacing:-.02em;
}
.nav-logo:hover{opacity:1;color:var(--accent)}
.nav-links{display:flex;gap:28px;align-items:center}
.nav-links a{
  font-size:.82rem;font-weight:450;color:var(--text-secondary);
  padding:4px 0;border-bottom:1.5px solid transparent;
  transition:all .25s;
}
.nav-links a:hover{color:var(--text);border-color:var(--accent);opacity:1}
.nav-links a.active{color:var(--text);border-color:var(--accent)}
.nav-toggle{display:none;background:none;border:none;cursor:pointer;padding:8px;color:var(--text)}

/* ---------- Section labels ---------- */
.section-label{
  font-size:.7rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:24px;
}

/* ---------- Hero ---------- */
.hero{
  padding:120px 0 80px;
  max-width:var(--reading-width);
}
.hero-eyebrow{
  font-size:.75rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:20px;
}
.hero h1{
  font-size:clamp(2.8rem,6vw,4.5rem);
  font-weight:600;letter-spacing:-.035em;line-height:1.05;
  margin-bottom:20px;color:var(--text);
}
.hero-sub{
  font-size:clamp(1rem,1.5vw,1.15rem);
  color:var(--text-secondary);line-height:1.8;
  margin-bottom:36px;max-width:540px;
}
.hero-cta{
  display:flex;gap:24px;flex-wrap:wrap;
}
.hero-cta a{
  font-size:.85rem;font-weight:500;
  display:inline-flex;align-items:center;gap:6px;
  padding-bottom:3px;
  border-bottom:1.5px solid transparent;
  color:var(--text-secondary);
}
.hero-cta a:hover{color:var(--accent);border-color:var(--accent);opacity:1}
.hero-cta a.primary{color:var(--accent)}

/* ---------- Section ---------- */
section{padding:120px 0}
section+section{border-top:1px solid var(--border)}

/* ---------- Featured Essay (home) ---------- */
.featured-card{
  background:var(--bg-secondary);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:40px;
  transition:all .3s;
  display:block;color:inherit;
}
.featured-card:hover{border-color:var(--accent);opacity:1}
.featured-card .tag{
  font-size:.65rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--accent);margin-bottom:12px;
}
.featured-card h2{
  font-family:var(--font-serif);
  font-size:1.35rem;font-weight:500;margin-bottom:10px;
  color:var(--text);
}
.featured-card p{font-size:.88rem;color:var(--text-secondary);line-height:1.6}
.featured-card .meta{
  font-size:.78rem;color:var(--text-tertiary);margin-top:16px;
  display:flex;gap:16px;
}

/* ---------- Latest Thinking (tweets/notes) ---------- */
.thinking-list{list-style:none}
.thinking-list li{
  padding:16px 0;
  border-bottom:1px solid var(--border);
  display:flex;gap:12px;align-items:flex-start;
}
.thinking-list li:last-child{border-bottom:none}
.thinking-dot{
  width:6px;height:6px;border-radius:50%;
  background:var(--accent);flex-shrink:0;margin-top:10px;
  opacity:.4;
}
.thinking-list a{color:var(--text);display:block;flex:1}
.thinking-list a:hover{opacity:1;color:var(--text)}
.thinking-list a p{font-size:.92rem;line-height:1.6}
.thinking-list .date{
  font-size:.72rem;color:var(--text-tertiary);margin-top:4px;
}

/* ---------- Current Reading ---------- */
.reading-item{
  display:flex;gap:16px;align-items:flex-start;
  padding:16px 0;border-bottom:1px solid var(--border);
}
.reading-item:last-child{border-bottom:none}
.reading-meta{font-size:.82rem;color:var(--text-tertiary);margin-bottom:2px}
.reading-item h4{font-size:.95rem;font-weight:450;margin-bottom:4px}
.reading-item h4 a{color:var(--text)}
.reading-item h4 a:hover{color:var(--accent);opacity:1}
.reading-item p{font-size:.82rem;color:var(--text-secondary)}

/* ---------- Project card (home/projects) ---------- */
.project-row{
  display:flex;justify-content:space-between;align-items:center;
  padding:20px 0;border-top:1px solid var(--border);
}
.project-row:last-of-type{border-bottom:1px solid var(--border)}
.project-row .tag{
  font-size:.65rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:3px;
}
.project-row h3{font-size:1rem;font-weight:500;color:var(--text)}
.project-link{
  font-size:.85rem;color:var(--text-secondary);
  display:inline-flex;align-items:center;gap:6px;
  transition:all .2s;
}
.project-link:hover{color:var(--accent);opacity:1}
.project-link svg{width:13px;height:13px;transition:transform .2s}
.project-link:hover svg{transform:translateX(3px)}
.projects-note{
  margin-top:20px;font-size:.85rem;color:var(--text-tertiary);
  font-style:italic;
}

/* ---------- Page Header (for sub-pages) ---------- */
.page-header{padding:80px 0 48px}
.page-header h1{
  font-size:clamp(2rem,4vw,2.8rem);
  font-weight:600;letter-spacing:-.03em;margin-bottom:12px;
}
.page-header p{font-size:1rem;max-width:540px;color:var(--text-secondary)}

/* ---------- Writing List ---------- */
.writing-list{max-width:var(--reading-width)}
.writing-item{
  padding:28px 0;
  border-bottom:1px solid var(--border);
  display:block;color:inherit;
}
.writing-item:first-child{padding-top:0}
.writing-item:hover{opacity:1}
.writing-item h2{
  font-family:var(--font-serif);
  font-size:1.15rem;font-weight:500;margin-bottom:8px;
  color:var(--text);transition:color .2s;
}
.writing-item:hover h2{color:var(--accent)}
.writing-item p{font-size:.88rem;color:var(--text-secondary);line-height:1.6;margin-bottom:10px}
.writing-meta{
  font-size:.78rem;color:var(--text-tertiary);
  display:flex;gap:16px;
}

/* ---------- Article Page ---------- */
.article-wrap{max-width:var(--reading-width);margin:0 auto;padding:60px 0 120px}
.article-header{margin-bottom:48px}
.article-header .breadcrumb{
  font-size:.78rem;color:var(--text-tertiary);margin-bottom:20px;
}
.article-header .breadcrumb a{color:var(--text-tertiary)}
.article-header .breadcrumb a:hover{color:var(--accent)}
.article-header h1{
  font-family:var(--font-serif);
  font-size:clamp(1.8rem,3.5vw,2.6rem);
  font-weight:500;letter-spacing:-.02em;line-height:1.2;
  margin-bottom:16px;
}
.article-meta{
  font-size:.82rem;color:var(--text-tertiary);
  display:flex;gap:20px;flex-wrap:wrap;
  padding-bottom:24px;border-bottom:1px solid var(--border);
}

/* ---------- TOC ---------- */
.toc{
  background:var(--bg-secondary);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:20px 24px;
  margin-bottom:48px;
}
.toc-label{
  font-size:.72rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:10px;
}
.toc-list{list-style:none;padding:0}
.toc-list li{margin-bottom:4px}
.toc-list a{
  font-size:.85rem;color:var(--text-secondary);
  display:inline-block;padding:3px 0;
  border-bottom:1px solid transparent;
}
.toc-list a:hover{color:var(--accent);border-color:var(--accent);opacity:1}

/* ---------- Article body ---------- */
.article-body{
  font-size:1rem;line-height:1.85;color:var(--text);
}
.article-body h2{
  font-size:1.35rem;font-weight:500;letter-spacing:-.01em;
  margin:48px 0 16px;padding-top:8px;
}
.article-body h3{
  font-size:1.1rem;font-weight:500;
  margin:32px 0 12px;
}
.article-body p{margin-bottom:20px;color:var(--text)}
.article-body blockquote{
  margin:28px 0;padding:20px 24px;
  border-left:3px solid var(--accent);
  background:var(--bg-secondary);
  border-radius:0 var(--radius) var(--radius) 0;
  font-family:var(--font-serif);
  font-style:italic;font-size:1.02rem;color:var(--text);
}
.article-body blockquote p{color:var(--text);margin-bottom:0}
.article-body hr{
  border:none;border-top:1px solid var(--border);
  margin:48px 0;
}
.article-body strong{font-weight:600}
.article-body em{font-style:italic}
.article-body a{border-bottom:1px solid var(--border)}
.article-body a:hover{border-color:var(--accent)}

/* ---------- Reading progress bar ---------- */
.progress-bar{
  position:fixed;top:var(--nav-height);left:0;width:100%;height:2px;
  z-index:99;background:transparent;
  pointer-events:none;
}
.progress-fill{
  height:100%;width:0;
  background:var(--accent);
  transition:width .1s linear;
}

/* ---------- Article footer (prev/next, related) ---------- */
.article-footer{margin-top:80px;padding-top:40px;border-top:1px solid var(--border)}
.article-nav{
  display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-bottom:48px;
}
.article-nav a{
  padding:20px;border:1px solid var(--border);
  border-radius:var(--radius);transition:all .25s;
}
.article-nav a:hover{border-color:var(--accent);opacity:1}
.article-nav .nav-label{
  font-size:.7rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:6px;
}
.article-nav .nav-title{
  font-size:.9rem;font-weight:450;color:var(--text);
}
.article-nav a.next{text-align:right}
.related-articles h3{
  font-size:.72rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:16px;
}
.related-list{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.related-list a{
  font-size:.88rem;padding:14px 18px;
  border:1px solid var(--border);border-radius:var(--radius);
  color:var(--text-secondary);transition:all .25s;
}
.related-list a:hover{border-color:var(--accent);color:var(--text);opacity:1}

/* ---------- Projects page ---------- */
.project-card{
  border:1px solid var(--border);border-radius:var(--radius);
  padding:32px;margin-bottom:20px;
  display:block;color:inherit;
  transition:all .3s;
}
.project-card:hover{border-color:var(--accent);opacity:1}
.project-card .tag{
  font-size:.65rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--accent);margin-bottom:8px;
}
.project-card h2{font-size:1.2rem;font-weight:500;margin-bottom:8px;color:var(--text)}
.project-card p{font-size:.88rem;color:var(--text-secondary);line-height:1.6;margin-bottom:16px}
.project-card .meta{
  font-size:.82rem;color:var(--text-tertiary);display:flex;gap:16px;
}

/* ---------- About page ---------- */
.about-content{max-width:var(--reading-width)}
.about-content section{margin-bottom:40px;border-top:none;padding:0}
.about-content h2{
  font-size:.75rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:16px;
}
.about-content p{
  font-size:1rem;color:var(--text);line-height:1.8;margin-bottom:16px;
}
.about-content .links{display:flex;gap:20px;flex-wrap:wrap}
.about-content .links a{
  font-size:.9rem;color:var(--text-secondary);
  display:flex;align-items:center;gap:6px;
}
.about-content .links a:hover{color:var(--accent);opacity:1}
.about-content .links svg{width:16px;height:16px}

/* ---------- Now page ---------- */
.now-content{max-width:var(--reading-width)}
.now-item{margin-bottom:48px}
.now-item:last-child{margin-bottom:0}
.now-item h2{
  font-size:.75rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--accent);margin-bottom:12px;
}
.now-item ul{list-style:none;padding:0}
.now-item li{
  padding:10px 0;border-bottom:1px solid var(--border);
  font-size:.95rem;color:var(--text);
  display:flex;gap:10px;align-items:flex-start;
}
.now-item li:last-child{border-bottom:none}
.now-item li::before{
  content:'-';color:var(--text-tertiary);margin-right:4px
}

/* ---------- Footer ---------- */
.footer{
  border-top:1px solid var(--border);
  padding:40px 0 48px;margin-top:80px;
}
.footer-inner{
  max-width:var(--max-width);margin:0 auto;padding:0 40px;
  display:flex;justify-content:space-between;align-items:center;
}
.footer-links{display:flex;gap:24px}
.footer-links a{
  font-size:.82rem;color:var(--text-tertiary);
  display:inline-flex;align-items:center;gap:6px;
}
.footer-links a:hover{color:var(--accent);opacity:1}
.footer-links svg{width:15px;height:15px}
.footer-copy{font-size:.75rem;color:var(--text-tertiary)}

/* ---------- Current Build (home) ---------- */
.current-build-card{
  background:var(--bg-secondary);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:40px;
  transition:all .3s;
}
.current-build-card .tag{
  font-size:.65rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--accent);margin-bottom:16px;
}
.current-build-card h2{
  font-family:var(--font-sans);
  font-size:1.25rem;font-weight:500;margin-bottom:6px;color:var(--text);
}
.current-build-card a{color:var(--text-secondary);font-size:.85rem}
.current-build-card a:hover{color:var(--accent);opacity:1}
.build-status{display:flex;align-items:center;gap:8px;margin-bottom:20px}
.build-dot{width:8px;height:8px;border-radius:50%;background:var(--accent);flex-shrink:0}
.build-status-text{font-size:.82rem;color:var(--text-secondary)}
.build-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px;margin-top:20px}
.build-grid h3{
  font-size:.7rem;font-weight:500;letter-spacing:.1em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:10px;
}
.build-grid ul{list-style:none;padding:0}
.build-grid li{
  font-size:.88rem;color:var(--text-secondary);padding:4px 0;
  display:flex;gap:8px;align-items:center;
}
.build-grid li::before{content:'—';color:var(--text-tertiary)}

/* ---------- Research Topics (home) ---------- */
.topic-row{
  display:flex;align-items:center;justify-content:space-between;
  padding:18px 20px;border:1px solid var(--border);
  border-radius:var(--radius);color:inherit;
  transition:all .25s;margin-bottom:10px;
}
.topic-row:hover{border-color:var(--accent);opacity:1}
.topic-row-info{display:flex;align-items:center;gap:12px}
.topic-row-count{
  font-size:.7rem;font-weight:500;color:var(--text-tertiary);
  background:var(--bg-secondary);padding:2px 10px;border-radius:20px;
}
.topic-row-link{
  font-size:.78rem;color:var(--text-tertiary);display:flex;align-items:center;gap:4px;
  transition:all .2s;
}
.topic-row:hover .topic-row-link{color:var(--accent)}
.topic-row-link svg{width:12px;height:12px;transition:transform .2s}
.topic-row:hover .topic-row-link svg{transform:translateX(3px)}

/* ---------- Research Page ---------- */
.research-intro{max-width:var(--reading-width);margin-bottom:48px}
.research-intro p{font-size:1rem;color:var(--text-secondary);line-height:1.7}
.research-card{
  border:1px solid var(--border);border-radius:var(--radius);
  padding:32px;margin-bottom:16px;display:block;color:inherit;
  transition:all .3s;
}
.research-card:hover{border-color:var(--accent);opacity:1}
.research-card h2{font-size:1.15rem;font-weight:500;margin-bottom:8px;color:var(--text)}
.research-card p{font-size:.85rem;color:var(--text-secondary);line-height:1.6;margin-bottom:16px}
.research-card .meta{
  font-size:.78rem;color:var(--text-tertiary);
  display:flex;gap:16px;align-items:center;
}
.research-card .read-link{
  font-size:.78rem;color:var(--accent);display:flex;align-items:center;gap:4px;
}

/* ---------- Content Relationships ---------- */
.related-projects{margin-top:40px;padding-top:32px;border-top:1px solid var(--border)}
.related-projects h3{
  font-size:.72rem;font-weight:500;letter-spacing:.12em;text-transform:uppercase;
  color:var(--text-tertiary);margin-bottom:16px;
}

/* ---------- Fade-up animation ---------- */
.fade-up{opacity:0;transform:translateY(16px);transition:opacity .6s ease,transform .6s var(--ease)}
.fade-up.visible{opacity:1;transform:translateY(0)}

/* ---------- Mobile ---------- */
@media(max-width:900px){
  .nav-links{gap:20px}
  .topic-grid{grid-template-columns:1fr 1fr}
  .related-list{grid-template-columns:1fr}
}
@media(max-width:768px){
  .container,.nav-inner,.footer-inner,.page-header{padding-left:24px;padding-right:24px}
  .hero{padding:80px 0 60px}
  section{padding:60px 0}
  .nav-links{
    position:fixed;top:var(--nav-height);left:0;right:0;
    background:rgba(255,255,255,.98);backdrop-filter:blur(12px);
    flex-direction:column;padding:20px 24px;gap:16px;
    border-bottom:1px solid var(--border);
    transform:translateY(-120%);opacity:0;
    transition:all .35s var(--ease);pointer-events:none;
  }
  .nav-links.open{transform:translateY(0);opacity:1;pointer-events:auto}
  .nav-toggle{display:block}
  .featured-card{padding:28px}
  .project-row{flex-direction:column;align-items:flex-start;gap:6px}
  .article-nav{grid-template-columns:1fr}
  .article-nav a.next{text-align:left}
  .footer-inner{flex-direction:column;gap:16px;text-align:center}
  .topic-grid{grid-template-columns:1fr}
}
@media(max-width:500px){
  .container,.nav-inner,.footer-inner,.page-header{padding-left:16px;padding-right:16px}
  .hero{padding:60px 0 48px}
  section{padding:48px 0}
  .hero-cta{flex-direction:column;gap:14px}
  .featured-card{padding:24px}
  .article-wrap{padding:40px 0 80px}
  .writing-item{padding:20px 0}
  .footer-links{flex-direction:column;gap:14px;align-items:center}
}
@media(prefers-reduced-motion:reduce){
  .fade-up{opacity:1;transform:none;transition:none}
  html{scroll-behavior:auto}
}