/* ============================================================
   BLOG ARTICLE — 共通スタイル
   ============================================================ */
@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@300;400;500;600;700;900&family=Inter:wght@400;600;700;800&display=swap');

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

:root {
  --clr-dark:       #0f172a;
  --clr-dark-2:     #1e293b;
  --clr-primary:    #f97316;
  --clr-accent:     #f97316;
  --clr-white:      #f8fafc;
  --clr-text:       #e2e8f0;
  --clr-text-sub:   #94a3b8;
  --clr-text-mute:  #64748b;
  --ff-jp:  'Noto Sans JP', sans-serif;
  --ff-eng: 'Inter', sans-serif;
  --radius-md: 10px;
  --radius-lg: 16px;
  --container: 800px;
  --transition: .25s ease;
}

html { scroll-behavior: smooth; }
body {
  font-family: var(--ff-jp);
  background: var(--clr-dark);
  color: var(--clr-text);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--clr-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

img { max-width: 100%; height: auto; display: block; border-radius: var(--radius-md); }

/* ============================================================
   HEADER
   ============================================================ */
.blog-header {
  background: rgba(15,23,42,.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(249,115,22,.2);
  padding: .9rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
}
.blog-header__inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.blog-header__logo {
  display: flex;
  align-items: center;
  gap: .5rem;
  font-family: var(--ff-eng);
  font-weight: 800;
  font-size: 1.1rem;
  color: var(--clr-primary);
  text-decoration: none;
}
.blog-header__logo span { color: var(--clr-text); font-weight: 400; font-size: .85rem; }
.blog-header__back {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  font-size: .82rem;
  color: var(--clr-text-sub);
  transition: color var(--transition);
}
.blog-header__back:hover { color: var(--clr-primary); text-decoration: none; }

/* ============================================================
   HERO (記事アイキャッチ)
   ============================================================ */
.article-hero {
  width: 100%;
  max-height: 480px;
  overflow: hidden;
  position: relative;
}
.article-hero img {
  width: 100%;
  height: 480px;
  object-fit: cover;
  object-position: center;
  border-radius: 0;
}
.article-hero__overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, rgba(15,23,42,0) 40%, rgba(15,23,42,.9) 100%);
}

/* ============================================================
   CONTAINER / LAYOUT
   ============================================================ */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ============================================================
   ARTICLE META
   ============================================================ */
.article-meta {
  padding: 2.5rem 0 1.5rem;
}
.article-meta__tag {
  display: inline-block;
  background: rgba(249,115,22,.15);
  border: 1px solid rgba(249,115,22,.35);
  color: var(--clr-primary);
  font-size: .75rem;
  font-weight: 700;
  padding: .3rem .9rem;
  border-radius: 50px;
  letter-spacing: .06em;
  margin-bottom: 1rem;
}
.article-meta__date {
  font-size: .82rem;
  color: var(--clr-text-mute);
  margin-top: .5rem;
  display: flex;
  align-items: center;
  gap: .4rem;
}

/* ============================================================
   ARTICLE TITLE
   ============================================================ */
.article-title {
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-weight: 800;
  line-height: 1.45;
  color: var(--clr-white);
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid #1e293b;
}

/* ============================================================
   ARTICLE BODY
   ============================================================ */
.article-body {
  padding-bottom: 4rem;
}
.article-body h2 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--clr-white);
  margin: 2.5rem 0 1rem;
  padding-left: 1rem;
  border-left: 4px solid var(--clr-primary);
}
.article-body h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin: 2rem 0 .75rem;
}
.article-body p {
  color: var(--clr-text);
  margin-bottom: 1.4rem;
  font-size: .97rem;
  line-height: 1.9;
}
.article-body strong { color: var(--clr-white); font-weight: 700; }
.article-body ul {
  list-style: none;
  margin-bottom: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: .5rem;
}
.article-body ul li {
  padding-left: 1.4rem;
  position: relative;
  color: var(--clr-text);
  font-size: .95rem;
}
.article-body ul li::before {
  content: '';
  position: absolute;
  left: 0;
  top: .65em;
  width: 7px; height: 7px;
  background: var(--clr-primary);
  border-radius: 50%;
}
.article-body figure {
  margin: 2rem 0;
}
.article-body figure img {
  width: 100%;
  border-radius: var(--radius-md);
  border: 1px solid #1e293b;
}
.article-body hr {
  border: none;
  border-top: 1px solid #1e293b;
  margin: 2.5rem 0;
}

/* ============================================================
   HIGHLIGHT BOX
   ============================================================ */
.highlight-box {
  background: rgba(249,115,22,.07);
  border: 1px solid rgba(249,115,22,.25);
  border-radius: var(--radius-md);
  padding: 1.5rem 1.75rem;
  margin: 2rem 0;
}
.highlight-box p { margin-bottom: 0; }

/* ============================================================
   BACK BUTTON (記事下部)
   ============================================================ */
.article-footer {
  padding: 3rem 0 5rem;
  border-top: 1px solid #1e293b;
  text-align: center;
}
.btn-back {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  background: transparent;
  border: 2px solid var(--clr-primary);
  color: var(--clr-primary);
  font-weight: 700;
  font-size: .92rem;
  padding: .8rem 2rem;
  border-radius: 50px;
  transition: all var(--transition);
  text-decoration: none;
}
.btn-back:hover {
  background: var(--clr-primary);
  color: #fff;
  text-decoration: none;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 600px) {
  .article-hero img { height: 260px; }
  .article-title { font-size: 1.25rem; }
  .article-body h2 { font-size: 1.1rem; }
}