:root {
  --bg: #ecfbff;
  --surface: rgba(255, 255, 255, 0.9);
  --surface-alt: #e5f7ff;
  --text: #17384a;
  --muted: #4f7080;
  --primary: #0ea5b7;
  --primary-dark: #0b7f8d;
  --border: #c6eaf2;
  --shadow: 0 12px 30px rgba(16, 84, 102, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", "Hiragino Kaku Gothic ProN", "Meiryo", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  position: relative;
  overflow-x: hidden;
}

body::before,
body::after {
  content: "";
  position: fixed;
  inset: -18%;
  pointer-events: none;
  z-index: 0;
}

body::before {
  background:
    radial-gradient(circle at 16% 20%, rgba(56, 189, 248, 0.3) 0%, transparent 36%),
    radial-gradient(circle at 78% 26%, rgba(45, 212, 191, 0.3) 0%, transparent 34%),
    radial-gradient(circle at 42% 80%, rgba(125, 211, 252, 0.28) 0%, transparent 35%);
  animation: driftA 22s ease-in-out infinite alternate;
}

body::after {
  background:
    radial-gradient(circle at 68% 72%, rgba(103, 232, 249, 0.24) 0%, transparent 32%),
    radial-gradient(circle at 24% 64%, rgba(110, 231, 183, 0.24) 0%, transparent 34%);
  animation: driftB 26s ease-in-out infinite alternate;
}

@keyframes driftA {
  0% {
    transform: translate3d(-1.5%, -1%, 0) scale(1);
  }
  100% {
    transform: translate3d(2%, 1.4%, 0) scale(1.08);
  }
}

@keyframes driftB {
  0% {
    transform: translate3d(1%, -1.2%, 0) scale(1.02);
  }
  100% {
    transform: translate3d(-2%, 1.6%, 0) scale(1.1);
  }
}

a {
  color: var(--primary-dark);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.site-header {
  padding: 1rem 0;
  border-bottom: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.78);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 20;
}


.hero,
.blog-layout,
.article,
.site-footer {
  position: relative;
  z-index: 1;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.logo {
  font-weight: 700;
  color: var(--text);
}

.nav {
  display: flex;
  gap: 1rem;
  font-size: 0.95rem;
}

.hero {
  padding: 3rem 0 1.2rem;
}

.hero-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 2rem;
  box-shadow: var(--shadow);
}

.hero h1 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: clamp(1.8rem, 4vw, 2.4rem);
  line-height: 1.3;
}

.hero p {
  margin: 0;
  color: var(--muted);
}

.blog-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  gap: 1.2rem;
  align-items: start;
  padding-bottom: 1.5rem;
}

.main-column {
  min-width: 0;
}

.section {
  padding: 0.5rem 0 1.4rem;
}

.section h2 {
  margin-bottom: 0.9rem;
  font-size: 1.35rem;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.2rem;
  box-shadow: var(--shadow);
}

.card h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.1rem;
}

.meta {
  color: var(--muted);
  font-size: 0.9rem;
  margin-bottom: 0.75rem;
}

.featured {
  border-left: 6px solid var(--primary);
}

.button {
  display: inline-block;
  margin-top: 0.75rem;
  background: linear-gradient(135deg, var(--primary) 0%, #22c7db 100%);
  color: #ffffff;
  padding: 0.55rem 0.9rem;
  border-radius: 10px;
  font-weight: 600;
}

.button:hover {
  background: linear-gradient(135deg, var(--primary-dark) 0%, #14a8bc 100%);
  text-decoration: none;
}

.category-block {
  margin-bottom: 1rem;
}

.link-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.link-list li {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  align-items: center;
  border-top: 1px dashed var(--border);
  padding: 0.6rem 0;
}

.link-list li:first-child {
  border-top: 0;
  padding-top: 0.2rem;
}

.date-chip {
  color: var(--muted);
  font-size: 0.82rem;
  white-space: nowrap;
}

.archive-sidebar {
  position: sticky;
  top: 86px;
}

.archive-card h2 {
  margin-top: 0;
  margin-bottom: 0.8rem;
  font-size: 1.1rem;
}

.archive-card details {
  margin-bottom: 0.6rem;
}

.archive-card summary {
  cursor: pointer;
  font-weight: 600;
}

.tree-list,
.tree-list ul {
  list-style: none;
  margin: 0.5rem 0 0;
  padding-left: 1rem;
  border-left: 1px solid var(--border);
}

.tree-list li {
  margin: 0.45rem 0;
}

.site-footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.article {
  padding: 2.2rem 0 3rem;
}

.article .content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 2rem;
}

.article h1 {
  line-height: 1.35;
}

.article h2 {
  margin-top: 1.8rem;
  margin-bottom: 0.7rem;
}

.article ul {
  padding-left: 1.2rem;
}

.article li {
  margin-bottom: 0.35rem;
}

.article pre {
  background: #113244;
  color: #e6f8ff;
  padding: 0.9rem;
  border-radius: 10px;
  overflow-x: auto;
}

.article code {
  font-family: Consolas, "Courier New", monospace;
}

@media (max-width: 980px) {
  .blog-layout {
    grid-template-columns: 1fr;
  }

  .archive-sidebar {
    position: static;
  }

  .header-inner {
    flex-direction: column;
    align-items: flex-start;
  }

  .hero {
    padding-top: 2rem;
  }
}


/* readability tuning: keep generous side margins on article pages */
.article .content {
  max-width: 780px;
  margin: 0 auto;
}