/* ============================================================
   style.css — 中森皇貴 ポートフォリオサイト
   構成:
     1. CSS Variables
     2. Reset
     3. Typography
     4. Layout Helpers
     5. Fade-in Animation
     6. Buttons
     7. Header / Nav
     8. Hero
     9. Services
    10. Works
    11. About
    12. Skills
    13. Contact
    14. Footer
    15. Scroll-to-top
    16. Responsive
============================================================ */

/* ===================== 1. CSS Variables ===================== */
:root {
  --bg:        #0F172A;
  --surface:   #1E293B;
  --surface2:  #263348;
  --accent:    #6366F1;
  --accent-lt: #818CF8;
  --light-bg:  #F8FAFC;
  --txt:       #F1F5F9;
  --txt-sub:   #94A3B8;
  --txt-dark:  #0F172A;
  --border:    rgba(255,255,255,0.08);
  --radius:    12px;
  --radius-lg: 20px;
  --shadow:    0 4px 24px rgba(0,0,0,0.35);
  --transition: 0.3s cubic-bezier(0.4,0,0.2,1);
}

/* ===================== 2. Reset ===================== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body {
  font-family: 'Noto Sans JP', 'Inter', sans-serif;
  background: var(--bg);
  color: var(--txt);
  line-height: 1.7;
  overflow-x: hidden;
}
img { max-width: 100%; display: block; }
a { text-decoration: none; color: inherit; }
ul { list-style: none; }
button { cursor: pointer; font-family: inherit; }

/* ===================== 3. Typography ===================== */
.section-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  color: var(--accent-lt);
  text-transform: uppercase;
  margin-bottom: 0.5rem;
}
.section-title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  line-height: 1.25;
  margin-bottom: 1rem;
}
.section-desc {
  color: var(--txt-sub);
  font-size: 1rem;
  max-width: 560px;
  line-height: 1.8;
}
.section-header { margin-bottom: 3rem; }

/* ===================== 4. Layout Helpers ===================== */
.container {
  width: 90%;
  max-width: 1100px;
  margin: 0 auto;
}
section { padding: 6rem 0; }

/* ===================== 5. Fade-in Animation ===================== */
.fade-in {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.65s ease, transform 0.65s ease;
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}
.fade-in-delay-1 { transition-delay: 0.1s; }
.fade-in-delay-2 { transition-delay: 0.2s; }
.fade-in-delay-3 { transition-delay: 0.3s; }
.fade-in-delay-4 { transition-delay: 0.4s; }

/* ===================== 6. Buttons ===================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.75rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  transition: var(--transition);
  border: none;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 0 20px rgba(99,102,241,0.35);
}
.btn-primary:hover {
  background: var(--accent-lt);
  box-shadow: 0 0 30px rgba(99,102,241,0.55);
  transform: translateY(-2px);
}
.btn-outline {
  background: transparent;
  color: var(--txt);
  border: 1.5px solid var(--border);
}
.btn-outline:hover {
  border-color: var(--accent-lt);
  color: var(--accent-lt);
  transform: translateY(-2px);
}

/* ===================== 7. Header / Nav ===================== */
header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  padding: 1.1rem 0;
  transition: background 0.35s, backdrop-filter 0.35s, box-shadow 0.35s;
}
header.scrolled {
  background: rgba(15,23,42,0.82);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  box-shadow: 0 1px 0 var(--border);
}
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-logo {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--accent-lt);
  letter-spacing: 0.05em;
}
.nav-links {
  display: flex;
  gap: 2rem;
  align-items: center;
}
.nav-links a {
  font-size: 0.9rem;
  color: var(--txt-sub);
  transition: color var(--transition);
  font-weight: 500;
}
.nav-links a:hover { color: var(--txt); }
.nav-cta {
  background: var(--accent);
  color: #fff !important;
  padding: 0.5rem 1.2rem;
  border-radius: 7px;
  font-weight: 600 !important;
  transition: background var(--transition) !important;
}
.nav-cta:hover { background: var(--accent-lt) !important; color: #fff !important; }
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  padding: 4px;
}
.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--txt);
  border-radius: 2px;
  transition: var(--transition);
}
.hamburger.open span:nth-child(1) { transform: rotate(45deg) translate(5px,5px); }
.hamburger.open span:nth-child(2) { opacity: 0; }
.hamburger.open span:nth-child(3) { transform: rotate(-45deg) translate(5px,-5px); }
.mobile-menu {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(15,23,42,0.97);
  z-index: 99;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2.5rem;
}
.mobile-menu.open { display: flex; }
.mobile-menu a {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--txt);
}
.mobile-menu a:hover { color: var(--accent-lt); }

/* ===================== 8. Hero ===================== */
#hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  padding: 7rem 0 4rem;
}
.hero-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
}
.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(99,102,241,0.12);
  border: 1px solid rgba(99,102,241,0.3);
  border-radius: 99px;
  padding: 0.35rem 1rem;
  font-size: 0.8rem;
  color: var(--accent-lt);
  margin-bottom: 1.5rem;
  font-family: 'JetBrains Mono', monospace;
}
.hero-badge::before { content: "▶"; font-size: 0.6rem; }
.hero-title {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 900;
  line-height: 1.2;
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
}
.hero-title .accent { color: var(--accent-lt); }
#typewriter { border-right: 2px solid var(--accent-lt); }
.hero-sub {
  color: var(--txt-sub);
  font-size: 1rem;
  line-height: 1.85;
  margin-bottom: 2rem;
}
.hero-sub strong { color: var(--txt); font-weight: 600; }
.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 2.5rem;
}
.hero-tag {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.3rem 0.75rem;
  font-size: 0.78rem;
  color: var(--txt-sub);
  font-family: 'JetBrains Mono', monospace;
}
.hero-btns {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Code decoration */
.hero-code {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  line-height: 1.85;
  position: relative;
  overflow: hidden;
}
.hero-code::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--accent-lt));
}
.hero-code .dots {
  display: flex;
  gap: 6px;
  margin-bottom: 1.25rem;
}
.hero-code .dots span {
  width: 10px; height: 10px;
  border-radius: 50%;
}
.hero-code .dots span:nth-child(1) { background: #FF5F57; }
.hero-code .dots span:nth-child(2) { background: #FFBD2E; }
.hero-code .dots span:nth-child(3) { background: #28CA41; }
.code-line    { display: block; }
.code-comment { color: #64748B; }
.code-keyword { color: #818CF8; }
.code-string  { color: #86EFAC; }
.code-func    { color: #7DD3FC; }
.code-num     { color: #FDA4AF; }

/* Background grid */
.hero-bg {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(99,102,241,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(99,102,241,0.04) 1px, transparent 1px);
  background-size: 60px 60px;
  pointer-events: none;
}
.hero-glow {
  position: absolute;
  width: 600px; height: 600px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(99,102,241,0.15) 0%, transparent 70%);
  top: -150px; right: -100px;
  pointer-events: none;
}

/* ===================== 9. Services ===================== */
#services { background: var(--bg); }
.services-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}
.service-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}
.service-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(99,102,241,0.06), transparent);
  opacity: 0;
  transition: opacity var(--transition);
}
.service-card:hover { transform: translateY(-4px); border-color: rgba(99,102,241,0.4); }
.service-card:hover::before { opacity: 1; }
.service-icon { font-size: 2rem; margin-bottom: 1rem; }
.service-card h3 { font-size: 1.05rem; font-weight: 700; margin-bottom: 0.6rem; }
.service-card p  { font-size: 0.875rem; color: var(--txt-sub); line-height: 1.75; }
.service-card .badge {
  display: inline-block;
  margin-top: 1rem;
  background: rgba(99,102,241,0.15);
  color: var(--accent-lt);
  border-radius: 4px;
  padding: 0.2rem 0.65rem;
  font-size: 0.72rem;
  font-family: 'JetBrains Mono', monospace;
}

/* ===================== 10. Works ===================== */
#works { background: var(--surface); }
.works-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(480px, 1fr));
  gap: 1.75rem;
}
.work-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem 2rem 1.5rem;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.work-card:hover { border-color: rgba(99,102,241,0.4); transform: translateY(-3px); box-shadow: var(--shadow); }
.work-card-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
}
.work-industry {
  font-size: 0.72rem;
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent-lt);
  background: rgba(99,102,241,0.12);
  border: 1px solid rgba(99,102,241,0.25);
  border-radius: 5px;
  padding: 0.2rem 0.65rem;
  white-space: nowrap;
}
.work-role {
  font-size: 0.72rem;
  color: var(--txt-sub);
  background: var(--surface);
  border-radius: 5px;
  padding: 0.2rem 0.65rem;
  white-space: nowrap;
}
.work-title { font-size: 1.05rem; font-weight: 700; line-height: 1.4; }
.work-meta  { display: flex; gap: 1.5rem; flex-wrap: wrap; }
.work-meta-item {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.8rem;
  color: var(--txt-sub);
}
.work-meta-item .label { color: var(--txt-sub); font-size: 0.72rem; }
.work-meta-item .value { color: var(--txt); font-weight: 500; }
.work-desc { font-size: 0.875rem; color: var(--txt-sub); line-height: 1.8; }
.work-desc strong { color: var(--txt); }
.work-tags  { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.work-tag {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: 0.2rem 0.6rem;
  font-size: 0.72rem;
  color: var(--txt-sub);
  font-family: 'JetBrains Mono', monospace;
}
.work-phases { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.phase-chip {
  font-size: 0.7rem;
  color: var(--accent-lt);
  background: rgba(99,102,241,0.1);
  border-radius: 4px;
  padding: 0.15rem 0.55rem;
}
.work-note {
  margin-top: 2.5rem;
  text-align: center;
  color: var(--txt-sub);
  font-size: 0.85rem;
  padding: 1.25rem;
  background: rgba(99,102,241,0.06);
  border: 1px solid rgba(99,102,241,0.15);
  border-radius: var(--radius);
}

/* ===================== 11. About ===================== */
#about { background: var(--light-bg); color: var(--txt-dark); }
#about .section-label { color: var(--accent); }
#about .section-title { color: var(--txt-dark); }
#about .section-desc  { color: #475569; }
.about-grid {
  display: grid;
  grid-template-columns: 340px 1fr;
  gap: 4rem;
  align-items: start;
}
.about-photo-wrap { position: relative; }
.about-photo {
  width: 100%;
  aspect-ratio: 4/5;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 12px 40px rgba(99,102,241,0.25);
  background: linear-gradient(135deg, #C7D2FE, #818CF8);
}
.about-photo img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center top;
  display: block;
}
.about-sns {
  display: flex;
  gap: 0.75rem;
  margin-top: 1.25rem;
  justify-content: center;
  flex-wrap: wrap;
}
.sns-btn {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.55rem 1rem;
  border-radius: 8px;
  font-size: 0.82rem;
  font-weight: 600;
  transition: var(--transition);
  border: 1.5px solid transparent;
}
.sns-instagram { background: linear-gradient(135deg,#f09433,#e6683c,#dc2743,#cc2366,#bc1888); color: #fff; }
.sns-github    { background: #1F2937; color: #F1F5F9; }
.sns-note      { background: #41C9B4; color: #fff; }
.sns-btn:hover { transform: translateY(-2px); box-shadow: 0 4px 16px rgba(0,0,0,0.2); }
.about-content h3 { font-size: 1.5rem; font-weight: 800; color: var(--txt-dark); margin-bottom: 0.25rem; }
.about-content .meta { font-size: 0.875rem; color: #64748B; margin-bottom: 2rem; font-family: 'JetBrains Mono', monospace; }
.about-block { margin-bottom: 2rem; }
.about-block h4 {
  font-size: 0.78rem;
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-bottom: 0.65rem;
}
.about-block p { font-size: 0.925rem; color: #334155; line-height: 1.85; }
.style-list { display: flex; flex-direction: column; gap: 0.5rem; }
.style-item {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.9rem;
  color: #334155;
}
.style-item::before {
  content: '';
  width: 6px; height: 6px;
  background: var(--accent);
  border-radius: 50%;
  flex-shrink: 0;
}

/* Walking trip callout */
.trip-callout {
  background: linear-gradient(135deg, #EEF2FF, #E0E7FF);
  border: 1.5px solid #C7D2FE;
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-top: 2rem;
  position: relative;
  overflow: hidden;
}
.trip-callout::before {
  content: '🚶';
  position: absolute;
  right: -10px; top: -10px;
  font-size: 5rem;
  opacity: 0.12;
}
.trip-title {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.95rem;
  font-weight: 800;
  color: var(--accent);
  margin-bottom: 0.6rem;
}
.trip-badge {
  background: var(--accent);
  color: #fff;
  font-size: 0.65rem;
  padding: 0.2rem 0.55rem;
  border-radius: 99px;
  font-family: 'JetBrains Mono', monospace;
  animation: pulse 2s infinite;
}
@keyframes pulse {
  0%,100% { opacity: 1; }
  50%      { opacity: 0.6; }
}
.trip-desc { font-size: 0.875rem; color: #475569; line-height: 1.75; margin-bottom: 1rem; }
.trip-links { display: flex; gap: 0.75rem; }
.trip-link {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  display: flex;
  align-items: center;
  gap: 0.3rem;
  transition: gap var(--transition);
}
.trip-link:hover { gap: 0.6rem; }

/* Certifications */
.cert-row { display: flex; gap: 0.6rem; flex-wrap: wrap; margin-top: 0.5rem; }
.cert-chip {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  background: #fff;
  border: 1px solid #E2E8F0;
  border-radius: 6px;
  padding: 0.35rem 0.8rem;
  font-size: 0.8rem;
  color: #334155;
  font-weight: 600;
}
.cert-chip .cert-icon { font-size: 1rem; }

/* ===================== 12. Skills ===================== */
#skills { background: var(--bg); }
.skills-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
}
.skill-group {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
}
.skill-group h3 {
  font-size: 0.72rem;
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent-lt);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-bottom: 1rem;
}
.skill-tags { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.skill-tag {
  padding: 0.4rem 0.85rem;
  border-radius: 6px;
  font-size: 0.78rem;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 500;
  transition: var(--transition);
}
.tag-a { background: rgba(99,102,241,0.18); color: #A5B4FC; border: 1px solid rgba(99,102,241,0.35); }
.tag-b { background: rgba(100,116,139,0.2);  color: #CBD5E1; border: 1px solid rgba(100,116,139,0.3); }
.tag-c { background: rgba(100,116,139,0.1);  color: #94A3B8; border: 1px solid rgba(100,116,139,0.18); }
.skill-tag:hover { transform: translateY(-1px); }
.skill-legend { display: flex; gap: 1.25rem; margin-bottom: 2.5rem; flex-wrap: wrap; }
.legend-item { display: flex; align-items: center; gap: 0.5rem; font-size: 0.78rem; color: var(--txt-sub); }
.legend-dot  { width: 10px; height: 10px; border-radius: 3px; }
.legend-a { background: rgba(99,102,241,0.6); }
.legend-b { background: rgba(100,116,139,0.5); }
.legend-c { background: rgba(100,116,139,0.25); }

/* Domain specialty */
.domain-row { display: flex; gap: 1rem; margin-top: 3rem; flex-wrap: wrap; }
.domain-card {
  flex: 1;
  min-width: 160px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  text-align: center;
  transition: var(--transition);
}
.domain-card:hover { border-color: rgba(99,102,241,0.4); }
.domain-card .icon  { font-size: 2rem; margin-bottom: 0.5rem; }
.domain-card .name  { font-size: 0.82rem; font-weight: 700; margin-bottom: 0.25rem; }
.domain-card .count { font-size: 0.72rem; color: var(--txt-sub); }

/* ===================== 13. Contact ===================== */
#contact { background: var(--surface); }
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 420px;
  gap: 4rem;
  align-items: start;
}
.contact-lead { font-size: 1rem; color: var(--txt-sub); line-height: 1.85; margin-bottom: 2rem; }
.contact-items { display: flex; flex-direction: column; gap: 1rem; margin-bottom: 2rem; }
.contact-item { display: flex; align-items: center; gap: 0.85rem; font-size: 0.875rem; color: var(--txt-sub); }
.contact-item .icon {
  width: 36px; height: 36px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  flex-shrink: 0;
}
.contact-social { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.social-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1.1rem;
  border-radius: 8px;
  font-size: 0.82rem;
  font-weight: 600;
  transition: var(--transition);
}
.social-link:hover { transform: translateY(-2px); }
.sl-ig   { background: linear-gradient(135deg,#f09433,#e6683c,#dc2743,#cc2366,#bc1888); color: #fff; }
.sl-gh   { background: var(--bg); border: 1px solid var(--border); color: var(--txt); }
.sl-gh:hover { border-color: var(--accent-lt); color: var(--accent-lt); }
.sl-note { background: #41C9B4; color: #fff; }
.contact-form {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
}
.form-group { margin-bottom: 1.25rem; }
.form-group label { display: block; font-size: 0.82rem; font-weight: 600; color: var(--txt-sub); margin-bottom: 0.5rem; }
.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem 1rem;
  color: var(--txt);
  font-size: 0.9rem;
  font-family: 'Noto Sans JP', sans-serif;
  transition: border-color var(--transition);
  outline: none;
}
.form-group input:focus,
.form-group textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99,102,241,0.15);
}
.form-group textarea { resize: vertical; min-height: 120px; }
.form-group input::placeholder,
.form-group textarea::placeholder { color: #475569; }
.form-submit {
  width: 100%;
  padding: 0.9rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
  font-family: 'Noto Sans JP', sans-serif;
}
.form-submit:hover { background: var(--accent-lt); box-shadow: 0 0 24px rgba(99,102,241,0.45); }
.form-note { text-align: center; font-size: 0.75rem; color: var(--txt-sub); margin-top: 0.75rem; }

/* ===================== 14. Footer ===================== */
footer {
  background: var(--bg);
  border-top: 1px solid var(--border);
  padding: 2.5rem 0;
  text-align: center;
}
.footer-catchcopy { font-size: 0.9rem; color: var(--txt-sub); margin-bottom: 1.25rem; }
.footer-links { display: flex; justify-content: center; gap: 1.5rem; margin-bottom: 1.25rem; flex-wrap: wrap; }
.footer-links a { font-size: 0.82rem; color: var(--txt-sub); transition: color var(--transition); }
.footer-links a:hover { color: var(--accent-lt); }
.footer-copy { font-size: 0.75rem; color: #475569; font-family: 'JetBrains Mono', monospace; }

/* ===================== 15. Scroll-to-top ===================== */
.scroll-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 44px; height: 44px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transition: var(--transition);
  z-index: 90;
  box-shadow: 0 4px 16px rgba(99,102,241,0.45);
}
.scroll-top.show { opacity: 1; pointer-events: all; }
.scroll-top:hover { transform: translateY(-3px); }

/* ===================== 16. Responsive ===================== */
@media (max-width: 900px) {
  .hero-grid    { grid-template-columns: 1fr; }
  .hero-code    { display: none; }
  .about-grid   { grid-template-columns: 1fr; }
  .about-photo  { aspect-ratio: 1/1; max-width: 280px; margin: 0 auto; }
  .contact-grid { grid-template-columns: 1fr; }
  .works-grid   { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  section { padding: 4rem 0; }
  .nav-links { display: none; }
  .hamburger { display: flex; }
  .hero-btns { flex-direction: column; }
  .hero-btns .btn { width: 100%; justify-content: center; }
  .domain-row { flex-direction: column; }
}