@import url('/css/style.css');

:root{
  --font-sans: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Inter, Arial, "Noto Sans", sans-serif;
  --max-w-article: 70ch;
  --space-1: .5rem;  /* 8px */
  --space-2: 1rem;   /* 16px */
  --space-3: 1.5rem; /* 24px */
  --space-4: 2rem;   /* 32px */
  --space-6: 3rem;   /* 48px */
  --clr-text: #0f172a;      /* slate-900 */
  --clr-muted: #475569;     /* slate-600 */
  --clr-accent: #2563eb;    /* blue-600 */
  --clr-border: #e2e8f0;    /* slate-200 */
  --radius: 14px;
}

/* Page container */
.article{
  font-family: var(--font-sans);
  color: var(--clr-text);
  margin: 0 auto;
  max-width: var(--max-w-article);
  padding: var(--space-4) var(--space-2) var(--space-6);
  line-height: 1.6;
}

/* Headings – uniform scale */
.article h1{
  font-weight: 800;
  line-height: 1.15;
  margin: 0 0 var(--space-3);
  font-size: clamp(2rem, 3.5vw, 2.6rem);
}
.article h2{
  font-weight: 800;
  line-height: 1.2;
  margin: var(--space-6) 0 var(--space-2);
  font-size: clamp(1.5rem, 2.8vw, 2rem);
  color: var(--clr-text);
  letter-spacing: -0.02em;
}
.article h3{
  font-weight: 600;
  margin: var(--space-4) 0 var(--space-2);
  font-size: clamp(1.1rem, 2vw, 1.25rem);
  color: var(--clr-muted);
  letter-spacing: 0;
}

/* Body content */
.article p{ margin: 0 0 var(--space-3); }
.article ul, .article ol{
  margin: 0 0 var(--space-3) var(--space-3);
  padding-left: var(--space-2);
}
.article li{
  margin: 0 0 .75rem;
  line-height: 1.7;
}
.article li strong{
  color: var(--clr-text);
}

/* Horizontal rule section breaks */
.article hr{
  border: none;
  border-top: 1px solid var(--clr-border);
  margin: var(--space-6) 0;
}

/* Callout/tip box */
.article .callout,
.article .tip{
  margin: var(--space-4) 0;
  padding: var(--space-3);
  background: #f0f9ff;
  border-left: 4px solid var(--clr-accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--clr-text);
}
.article .callout p:last-child,
.article .tip p:last-child{
  margin-bottom: 0;
}
.article em{ font-style: italic; }
.article strong{ font-weight: 800; }
.article blockquote{
  margin: var(--space-4) 0;
  padding: var(--space-2) var(--space-3);
  border-left: 4px solid var(--clr-accent);
  background: #f8fafc;
  border-radius: var(--radius);
  color: var(--clr-muted);
}

.article .formula{
  margin: var(--space-3) 0;
  padding: var(--space-2);
  background:#f8fafc;
  border:1px solid var(--clr-border);
  border-radius:var(--radius);
  font-family:'Courier New', Courier, monospace;
  font-size:.95rem;
  overflow-x:auto;
}

/* Images */
.article img{
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin: var(--space-3) 0;
}

/* Inline “highlight” helper (optional) */
.mark{ font-weight: 800; }

/* CTA footer block used on articles */
.article-footer{
  margin-top: var(--space-6);
  padding: var(--space-3);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  background: #ffffff;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.cta-actions{
  display:flex;
  flex-wrap:wrap;
  gap:var(--space-2);
}

/* CTA button */
.btn{
  display: inline-block;
  padding: .8rem 1.2rem;
  border-radius: 9999px;
  text-decoration: none;
  font-weight: 700;
  text-align: center;
  border: 1px solid transparent;
}
.btn-primary{
  background: var(--clr-accent);
  color: #fff;
}
.btn-primary:hover{ filter: brightness(0.95); }
.btn-secondary{
  background:#fff;
  color:var(--clr-accent);
  border-color:var(--clr-accent);
}
.btn-secondary:hover{
  background:rgba(37,99,235,0.08);
}

/* Site footer spacing so CTA never overlaps copyright */
.site-footer{
  margin-top: var(--space-6);
  padding-bottom: var(--space-4);
  position: static; /* ensure not absolute/fixed */
}

.breadcrumb{
  font-size:.9rem;
  margin-bottom:var(--space-2);
  color:var(--clr-muted);
}
.breadcrumb ol{
  list-style:none;
  padding:0;
  margin:0;
  display:flex;
  flex-wrap:wrap;
  gap:.35rem;
}
.breadcrumb li::after{
  content:'/';
  margin-left:.35rem;
  color:var(--clr-border);
}
.breadcrumb li:last-child::after{content:'';}
.breadcrumb-link{
  color:inherit;
  text-decoration:none;
}
.breadcrumb-link:hover{color:var(--clr-accent);}
.back-link{
  display:inline-flex;
  align-items:center;
  gap:.35rem;
  font-weight:600;
  color:var(--clr-accent);
  text-decoration:none;
  margin-bottom:var(--space-2);
}
.back-link:hover{text-decoration:underline;}
.article-summary{
  font-size:1.1rem;
  color:var(--clr-muted);
  margin-bottom:var(--space-3);
}

/* CLS Prevention: Reserve consistent hero dimensions */
.article-hero {
  aspect-ratio: 21/9;
  min-height: 280px; /* Fallback for browsers without aspect-ratio support */
  position: relative;
  overflow: hidden;
}

/* Dark gradient overlay for text readability on light images */
.article-hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0.3) 0%,
    rgba(0, 0, 0, 0.55) 100%
  );
  z-index: 1;
}

.article-hero .hero-inner {
  min-height: 160px; /* Reserve space for eyebrow + title (2-3 lines) + meta */
  position: relative;
  z-index: 2; /* Above the overlay */
}

/* Hero title text shadow for readability */
.article-hero h1 {
  text-shadow:
    0 2px 4px rgba(0, 0, 0, 0.5),
    0 4px 8px rgba(0, 0, 0, 0.3);
}

.article-hero img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  z-index: 0;
  /* Override .article img rules that would conflict */
  aspect-ratio: unset;
  margin: 0;
  border-radius: 0;
}

/* CLS Prevention: Reserve space for related sidebar */
.related-sidebar {
  min-height: 580px; /* ~5 cards × 108px + heading */
}

/* CLS Prevention: Reserve space for article body */
#article-body {
  min-height: 400px;
}

#article-body:not(:empty) {
  min-height: auto; /* Remove constraint once content loads */
}

/* CLS Prevention: Smooth visibility for summary */
.article-summary.is-hidden {
  visibility: hidden;
  height: 0;
  margin: 0;
  padding: 0;
  overflow: hidden;
}

@media (max-width: 860px) {
  .related-sidebar {
    min-height: auto; /* Don't reserve on mobile where sidebar reflows below */
  }

  /* Larger min-height on mobile to prevent article body expansion shifts */
  #article-body {
    min-height: 1200px;
  }

  #article-body:not(:empty) {
    min-height: auto;
  }
}

/* Prevent layout shifts from propagating outside article */
.article {
  contain: layout style;
}

.related-sidebar{
  display:flex;
  flex-direction:column;
  gap:var(--space-2);
}

.related-list{
  display:flex;
  flex-direction:column;
  gap:var(--space-2);
}

.related-card{
  display:flex;
  gap:var(--space-2);
  align-items:flex-start;
  text-decoration:none;
  padding:.5rem;
  border-radius:12px;
  background:#f8fafc;
  border:1px solid var(--clr-border);
  transition:transform .2s ease,box-shadow .2s ease,background .2s ease;
  color:inherit;
}

.related-card:hover{
  transform:translateY(-2px);
  box-shadow:0 12px 24px rgba(15,23,42,0.12);
  background:#fff;
}

.related-thumb{
  width:72px;
  height:72px;
  border-radius:12px;
  overflow:hidden;
  flex-shrink:0;
  background:#e2e8f0;
}

.related-thumb img{
  width:100%;
  height:100%;
  object-fit:cover;
  display:block;
}

.related-content{
  display:flex;
  flex-direction:column;
  gap:.35rem;
}

.related-tag{
  font-size:.75rem;
  text-transform:uppercase;
  letter-spacing:.08em;
  color:var(--clr-accent);
  font-weight:700;
}

.related-title{
  font-weight:700;
  line-height:1.35;
}

.related-read{
  font-size:.85rem;
  color:var(--clr-muted);
}

.related-empty{
  padding:1rem;
  border-radius:12px;
  background:#f8fafc;
  border:1px solid var(--clr-border);
  color:var(--clr-muted);
  font-size:.9rem;
}

/* Prevent overlap on small screens */
@media (max-width: 520px){
  .article{ padding-bottom: calc(var(--space-6) + 40px); }
}

@media (max-width: 860px){
  .two-col{grid-template-columns:1fr;}
  .related-sidebar{order:2;margin-top:var(--space-4);}
}

/* ========================================
   Series Navigation Components (Phase 2)
   ======================================== */

/* "In This Series" box - appears after intro in main article */
.series-box{
  margin: var(--space-4) 0;
  padding: var(--space-3);
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  border: 1px solid #bae6fd;
  border-radius: var(--radius);
}
.series-box-header{
  display: flex;
  align-items: center;
  gap: .5rem;
  font-size: .85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--clr-accent);
  margin-bottom: var(--space-2);
}
.series-box-list{
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: .75rem;
}
.series-box-item{
  margin: 0;
}
.series-box-link{
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: .75rem 1rem;
  background: #fff;
  border-radius: 10px;
  text-decoration: none;
  color: var(--clr-text);
  font-weight: 600;
  transition: transform .15s ease, box-shadow .15s ease;
  border: 1px solid transparent;
}
.series-box-link:hover{
  transform: translateX(4px);
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.15);
  border-color: var(--clr-accent);
}
.series-box-link span.read-time{
  font-size: .85rem;
  color: var(--clr-muted);
  font-weight: 500;
}

/* Series Cards Grid - appears before CTA at bottom of main article */
.series-cards-section{
  margin: var(--space-6) 0;
}
.series-cards-header{
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: var(--space-3);
  color: var(--clr-text);
}
.series-cards{
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-2);
}
.series-card{
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: var(--space-3);
  background: #f8fafc;
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--clr-text);
  transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease;
}
.series-card:hover{
  transform: translateY(-3px);
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.1);
  border-color: var(--clr-accent);
}
.series-card-title{
  font-weight: 700;
  font-size: 1rem;
  line-height: 1.4;
  margin-bottom: .5rem;
}
.series-card-meta{
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: .85rem;
  color: var(--clr-muted);
}
.series-card-arrow{
  color: var(--clr-accent);
  font-weight: 700;
  transition: transform .2s ease;
}
.series-card:hover .series-card-arrow{
  transform: translateX(4px);
}

@media (max-width: 600px){
  .series-cards{
    grid-template-columns: 1fr;
  }
}

/* Series Breadcrumb - appears at top of sub-articles */
.series-breadcrumb{
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem 1rem;
  margin-bottom: var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--clr-border);
  font-size: .9rem;
}
.series-breadcrumb-back{
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  color: var(--clr-accent);
  text-decoration: none;
  font-weight: 600;
}
.series-breadcrumb-back:hover{
  text-decoration: underline;
}
.series-breadcrumb-part{
  color: var(--clr-muted);
  font-weight: 500;
  padding: .25rem .75rem;
  background: #f1f5f9;
  border-radius: 9999px;
  font-size: .8rem;
}

/* Sidebar Series Navigation */
.sidebar-series{
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.sidebar-series-header{
  font-size: .8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--clr-accent);
  margin-bottom: .5rem;
}
.sidebar-series-main{
  display: flex;
  align-items: center;
  gap: .5rem;
  padding: .75rem;
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  border: 1px solid #bae6fd;
  border-radius: 10px;
  text-decoration: none;
  color: var(--clr-text);
  font-weight: 600;
  font-size: .95rem;
  transition: transform .15s ease;
}
.sidebar-series-main:hover{
  transform: translateX(2px);
}
.sidebar-series-main .icon{
  font-size: 1.1rem;
}
.sidebar-series-list{
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: .5rem;
}
.sidebar-series-item{
  margin: 0;
}
.sidebar-series-link{
  display: flex;
  align-items: center;
  gap: .5rem;
  padding: .6rem .75rem;
  background: #f8fafc;
  border: 1px solid var(--clr-border);
  border-radius: 8px;
  text-decoration: none;
  color: var(--clr-text);
  font-size: .9rem;
  font-weight: 500;
  line-height: 1.35;
  transition: background .15s ease, border-color .15s ease;
}
.sidebar-series-link:hover{
  background: #fff;
  border-color: var(--clr-accent);
}
.sidebar-series-link.is-current{
  background: #fff;
  border-color: var(--clr-accent);
  color: var(--clr-accent);
  font-weight: 700;
}
.sidebar-series-link .check{
  color: #22c55e;
  font-weight: 700;
}