/* =====================================================
   DESIGN SYSTEM — Joe Yang Personal Landing Page
   ===================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

/* ── CSS Variables ─────────────────────────────────── */
:root {
  --bg-deep:       #070b14;
  --bg-mid:        #0d1424;
  --bg-card:       rgba(255, 255, 255, 0.04);
  --bg-card-hover: rgba(255, 255, 255, 0.08);
  --border:        rgba(255, 255, 255, 0.08);
  --border-hover:  rgba(120, 100, 255, 0.5);

  --accent-purple: #7c5cfc;
  --accent-cyan:   #22d3ee;
  --accent-grad:   linear-gradient(135deg, #7c5cfc 0%, #22d3ee 100%);
  --accent-grad-text: linear-gradient(90deg, #a78bfa 0%, #38bdf8 100%);

  --text-primary:  #f0f4ff;
  --text-secondary:#94a3b8;
  --text-muted:    #4b5675;

  --nav-h:         68px;
  --radius-card:   16px;
  --radius-pill:   999px;

  --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  --transition:    0.3s var(--ease-out-expo);
}

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

/* ── Noise texture overlay ─────────────────────────── */
body::before {
  content: '';
  position: fixed; inset: 0; z-index: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)' opacity='0.04'/%3E%3C/svg%3E");
  pointer-events: none;
}

/* ── Ambient glow blobs ────────────────────────────── */
.glow-blob {
  position: fixed; border-radius: 50%;
  filter: blur(120px); opacity: 0.18; pointer-events: none; z-index: 0;
}
.glow-blob--purple { width: 600px; height: 600px; background: var(--accent-purple); top: -150px; left: -150px; }
.glow-blob--cyan   { width: 500px; height: 500px; background: var(--accent-cyan);   bottom: -100px; right: -100px; }

/* ── Navigation ────────────────────────────────────── */
nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: var(--nav-h);
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 clamp(1.5rem, 6vw, 5rem);
  background: rgba(7, 11, 20, 0.75);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition);
}
.nav-logo {
  font-size: 1.15rem; font-weight: 700; letter-spacing: -0.02em;
  background: var(--accent-grad-text); -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.nav-links {
  display: flex; gap: 2rem; align-items: center;
}
.nav-links a {
  font-size: 0.875rem; font-weight: 500; color: var(--text-secondary);
  transition: color var(--transition);
  position: relative;
}
.nav-links a::after {
  content: ''; position: absolute; bottom: -4px; left: 0; width: 0; height: 2px;
  background: var(--accent-grad); border-radius: 1px;
  transition: width var(--transition);
}
.nav-links a:hover { color: var(--text-primary); }
.nav-links a:hover::after { width: 100%; }

/* language + download buttons in nav */
.nav-actions { display: flex; align-items: center; gap: 0.75rem; }

.btn-lang {
  display: flex; align-items: center; gap: 0.4rem;
  padding: 0.4rem 1rem; border-radius: var(--radius-pill);
  font-size: 0.8rem; font-weight: 600; cursor: pointer;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-secondary);
  transition: all var(--transition);
}
.btn-lang:hover {
  border-color: var(--accent-purple); color: var(--text-primary);
  background: rgba(124, 92, 252, 0.12);
}

.btn-download {
  display: flex; align-items: center; gap: 0.45rem;
  padding: 0.45rem 1.1rem; border-radius: var(--radius-pill);
  font-size: 0.8rem; font-weight: 600; cursor: pointer;
  border: none;
  background: var(--accent-grad);
  color: #fff;
  transition: opacity var(--transition), transform var(--transition), box-shadow var(--transition);
  box-shadow: 0 4px 20px rgba(124, 92, 252, 0.35);
}
.btn-download:hover { opacity: 0.88; transform: translateY(-1px); box-shadow: 0 8px 30px rgba(124, 92, 252, 0.5); }
.btn-download svg, .btn-lang svg { width: 14px; height: 14px; flex-shrink: 0; }

/* ── Sections & layout ─────────────────────────────── */
main { position: relative; z-index: 1; }
section { padding: 6rem clamp(1.5rem, 8vw, 10rem); }
.container { max-width: 900px; margin: 0 auto; }

/* Section heading */
.section-label {
  font-size: 0.7rem; font-weight: 700; letter-spacing: 0.15em; text-transform: uppercase;
  color: var(--accent-purple); margin-bottom: 0.6rem;
}
.section-title {
  font-size: clamp(1.6rem, 4vw, 2.4rem); font-weight: 800; letter-spacing: -0.03em;
  color: var(--text-primary); margin-bottom: 3rem;
}

/* ── Hero ──────────────────────────────────────────── */
.hero {
  min-height: 100vh;
  display: flex; align-items: center;
  padding-top: calc(var(--nav-h) + 2rem);
}
.hero-inner {
  display: grid; grid-template-columns: 1fr auto; gap: 3rem;
  align-items: center; max-width: 900px; margin: 0 auto; width: 100%;
}
.hero-greeting {
  font-size: 0.85rem; font-weight: 600; letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--accent-cyan); margin-bottom: 1rem;
  display: flex; align-items: center; gap: 0.6rem;
}
.hero-greeting::before {
  content: ''; display: inline-block; width: 24px; height: 2px; background: var(--accent-cyan); border-radius: 1px;
}
.hero-name {
  font-size: clamp(2rem, 5vw, 3.8rem); font-weight: 800; letter-spacing: -0.04em;
  line-height: 1.05; margin-bottom: 1rem;
  background: var(--accent-grad-text); -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.hero-title {
  font-size: clamp(1rem, 2.5vw, 1.35rem); font-weight: 400; color: var(--text-secondary);
  margin-bottom: 0.75rem; max-width: 520px; line-height: 1.5;
}
.hero-location {
  display: flex; align-items: center; gap: 0.4rem;
  font-size: 0.85rem; color: var(--text-muted); margin-bottom: 2rem;
}
.hero-location svg { width: 14px; height: 14px; }

.hero-cta {
  display: flex; flex-wrap: wrap; gap: 0.75rem;
}
.btn-primary, .btn-secondary {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.75rem 1.75rem; border-radius: var(--radius-pill);
  font-size: 0.9rem; font-weight: 600; cursor: pointer;
  line-height: 1.2; white-space: nowrap;
  transition: all var(--transition);
}
.btn-primary svg, .btn-secondary svg {
  width: 18px; height: 18px; flex-shrink: 0;
}
.btn-primary {
  background: var(--accent-grad); color: #fff; border: none;
  box-shadow: 0 4px 24px rgba(124, 92, 252, 0.4);
}
.btn-primary:hover { opacity: 0.88; transform: translateY(-2px); box-shadow: 0 10px 36px rgba(124, 92, 252, 0.55); }
.btn-secondary {
  background: var(--bg-card); color: var(--text-secondary);
  border: 1px solid var(--border);
}
.btn-secondary:hover { border-color: var(--border-hover); color: var(--text-primary); background: var(--bg-card-hover); }

/* Avatar */
.hero-avatar {
  width: 180px; height: 180px; border-radius: 50%;
  position: relative; flex-shrink: 0;
}
.hero-avatar::before {
  content: ''; position: absolute; inset: -3px; border-radius: 50%;
  background: var(--accent-grad); z-index: -1;
  animation: spin-slow 8s linear infinite;
}
.hero-avatar img {
  width: 100%; height: 100%; border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--bg-deep);
}
.avatar-initials {
  width: 100%; height: 100%; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  background: linear-gradient(135deg, #1e1040 0%, #0d2040 100%);
  font-size: 3rem; font-weight: 800;
  background-clip: text; -webkit-background-clip: text;
  color: transparent;
  background: var(--accent-grad-text);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  border: 3px solid var(--bg-deep);
}

@keyframes spin-slow {
  from { transform: rotate(0deg); }
  to   { transform: rotate(360deg); }
}

/* Contact chips */
.hero-contacts {
  display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 1.75rem;
}
.contact-chip {
  display: flex; align-items: center; gap: 0.35rem;
  padding: 0.3rem 0.8rem; border-radius: var(--radius-pill);
  background: var(--bg-card); border: 1px solid var(--border);
  font-size: 0.75rem; color: var(--text-secondary);
  transition: all var(--transition);
}
.contact-chip:hover { border-color: var(--accent-purple); color: var(--text-primary); background: var(--bg-card-hover); }
.contact-chip svg { width: 12px; height: 12px; }

/* ── About ─────────────────────────────────────────── */
.about-section { background: var(--bg-mid); }
.about-text {
  font-size: 1.05rem; color: var(--text-secondary); line-height: 1.85;
  max-width: 750px;
}
.about-text strong { color: var(--text-primary); }

.stats-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1rem; margin-top: 2.5rem;
}
.stat-card {
  padding: 1.5rem; border-radius: var(--radius-card);
  background: var(--bg-card); border: 1px solid var(--border);
  transition: all var(--transition);
  backdrop-filter: blur(10px);
}
.stat-card:hover { border-color: var(--border-hover); background: var(--bg-card-hover); transform: translateY(-3px); }
.stat-number {
  font-size: 2rem; font-weight: 800;
  background: var(--accent-grad-text); -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  line-height: 1;
}
.stat-label { font-size: 0.78rem; color: var(--text-muted); margin-top: 0.35rem; }

/* ── Experience / Timeline ─────────────────────────── */
.timeline { position: relative; }
.timeline::before {
  content: ''; position: absolute; left: 0; top: 0; bottom: 0; width: 2px;
  background: linear-gradient(to bottom, var(--accent-purple), var(--accent-cyan));
  border-radius: 1px;
}

.timeline-item {
  position: relative; padding-left: 2.5rem; margin-bottom: 2.5rem;
}
.timeline-item::before {
  content: ''; position: absolute; left: -5px; top: 6px;
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--accent-purple);
  box-shadow: 0 0 0 3px var(--bg-deep), 0 0 0 5px rgba(124,92,252,0.3);
  transition: box-shadow var(--transition);
}
.timeline-item:hover::before { box-shadow: 0 0 0 3px var(--bg-deep), 0 0 0 8px rgba(124,92,252,0.4); }

.exp-card {
  padding: 1.75rem 2rem; border-radius: var(--radius-card);
  background: var(--bg-card); border: 1px solid var(--border);
  backdrop-filter: blur(12px);
  transition: all var(--transition);
}
.exp-card:hover { border-color: var(--border-hover); background: var(--bg-card-hover); transform: translateX(4px); }

.exp-company {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.1em; text-transform: uppercase;
  color: var(--accent-cyan); margin-bottom: 0.2rem;
}
.exp-title {
  font-size: 1.05rem; font-weight: 700; color: var(--text-primary); margin-bottom: 0.25rem;
}
.exp-meta {
  display: flex; flex-wrap: wrap; gap: 0.75rem;
  font-size: 0.78rem; color: var(--text-muted); margin-bottom: 1rem;
}
.exp-meta span { display: flex; align-items: center; gap: 0.25rem; }
.exp-bullets { display: flex; flex-direction: column; gap: 0.6rem; }
.exp-bullets li {
  font-size: 0.88rem; color: var(--text-secondary); line-height: 1.6;
  padding-left: 1.1rem; position: relative;
}
.exp-bullets li::before {
  content: '▸'; position: absolute; left: 0;
  color: var(--accent-purple); font-size: 0.7rem; top: 0.15rem;
}
.exp-highlight {
  color: var(--text-primary); font-weight: 600;
}

/* ── Skills ────────────────────────────────────────── */
.skills-section { background: var(--bg-mid); }
.skills-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 1.25rem;
}
.skill-group {
  padding: 1.5rem; border-radius: var(--radius-card);
  background: var(--bg-card); border: 1px solid var(--border);
  backdrop-filter: blur(10px);
  transition: all var(--transition);
}
.skill-group:hover { border-color: var(--border-hover); transform: translateY(-3px); }
.skill-group-title {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--accent-purple); margin-bottom: 1rem;
}
.skill-tags { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.skill-tag {
  padding: 0.25rem 0.7rem; border-radius: var(--radius-pill);
  background: rgba(124, 92, 252, 0.1); border: 1px solid rgba(124, 92, 252, 0.25);
  font-size: 0.78rem; color: var(--text-secondary);
  transition: all var(--transition);
}
.skill-tag:hover { background: rgba(124, 92, 252, 0.2); color: var(--text-primary); border-color: var(--accent-purple); }

/* ── Education ─────────────────────────────────────── */
.edu-card {
  display: flex; align-items: flex-start; gap: 1.5rem;
  padding: 1.75rem 2rem; border-radius: var(--radius-card);
  background: var(--bg-card); border: 1px solid var(--border);
  backdrop-filter: blur(12px); max-width: 600px;
  transition: all var(--transition);
}
.edu-card:hover { border-color: var(--border-hover); background: var(--bg-card-hover); }
.edu-icon {
  width: 48px; height: 48px; border-radius: 12px; flex-shrink: 0;
  background: linear-gradient(135deg, rgba(124,92,252,0.25), rgba(34,211,238,0.15));
  border: 1px solid rgba(124,92,252,0.3);
  display: flex; align-items: center; justify-content: center; font-size: 1.4rem;
}
.edu-school { font-size: 1rem; font-weight: 700; color: var(--text-primary); }
.edu-degree { font-size: 0.9rem; color: var(--text-secondary); }
.edu-date { font-size: 0.78rem; color: var(--text-muted); margin-top: 0.3rem; }

/* ── Contact / Footer ──────────────────────────────── */
.contact-section {
  text-align: center;
  border-top: 1px solid var(--border);
}
.contact-section .section-title { margin-bottom: 0.75rem; }
.contact-desc { color: var(--text-secondary); max-width: 520px; margin: 0 auto 2.5rem; }

/* Contact Form */
.contact-form {
  max-width: 580px; margin: 0 auto;
  display: flex; flex-direction: column; gap: 1rem;
  text-align: left;
}
.form-row {
  display: grid; grid-template-columns: 1fr 1fr; gap: 1rem;
}
@media (max-width: 540px) { .form-row { grid-template-columns: 1fr; } }

.form-group { display: flex; flex-direction: column; gap: 0.4rem; }
.form-group label {
  font-size: 0.78rem; font-weight: 600; letter-spacing: 0.06em;
  color: var(--text-secondary); text-transform: uppercase;
}
.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text-primary);
  font-family: inherit; font-size: 0.9rem;
  outline: none; resize: vertical;
  transition: border-color var(--transition), background var(--transition), box-shadow var(--transition);
  backdrop-filter: blur(8px);
}
.form-group input::placeholder,
.form-group textarea::placeholder { color: var(--text-muted); }
.form-group input:focus,
.form-group textarea:focus {
  border-color: var(--accent-purple);
  background: var(--bg-card-hover);
  box-shadow: 0 0 0 3px rgba(124, 92, 252, 0.15);
}
.form-group textarea { min-height: 130px; }

.btn-submit {
  display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem;
  padding: 0.85rem 2rem; border-radius: var(--radius-pill);
  font-size: 0.95rem; font-weight: 600; cursor: pointer; border: none;
  background: var(--accent-grad); color: #fff; white-space: nowrap;
  box-shadow: 0 4px 24px rgba(124, 92, 252, 0.4);
  transition: all var(--transition);
  align-self: flex-end;
}
.btn-submit svg { width: 18px; height: 18px; flex-shrink: 0; }
.btn-submit:hover:not(:disabled) { opacity: 0.88; transform: translateY(-2px); box-shadow: 0 10px 36px rgba(124, 92, 252, 0.55); }
.btn-submit:disabled { opacity: 0.55; cursor: not-allowed; }

/* Feedback messages */
.form-feedback {
  max-width: 580px; margin: 1rem auto 0;
  padding: 0.9rem 1.25rem; border-radius: 10px;
  font-size: 0.88rem; font-weight: 500; display: none;
}
.form-feedback.success {
  display: block;
  background: rgba(34, 197, 94, 0.12);
  border: 1px solid rgba(34, 197, 94, 0.35);
  color: #4ade80;
}
.form-feedback.error {
  display: block;
  background: rgba(239, 68, 68, 0.12);
  border: 1px solid rgba(239, 68, 68, 0.3);
  color: #f87171;
}

footer {
  text-align: center; padding: 2rem;
  font-size: 0.78rem; color: var(--text-muted);
  border-top: 1px solid var(--border);
  position: relative; z-index: 1;
}

/* ── Scroll reveal animation ───────────────────────── */
.reveal {
  opacity: 0; transform: translateY(28px);
  transition: opacity 0.7s var(--ease-out-expo), transform 0.7s var(--ease-out-expo);
}
.reveal.visible { opacity: 1; transform: translateY(0); }

/* ── Responsive ────────────────────────────────────── */
@media (max-width: 768px) {
  .hero-inner { grid-template-columns: 1fr; text-align: center; }
  .hero-avatar { width: 130px; height: 130px; margin: 0 auto; order: -1; }
  .hero-greeting { justify-content: center; }
  .hero-contacts { justify-content: center; }
  .hero-cta { justify-content: center; }
  .nav-links { display: none; }
  section { padding: 4rem 1.5rem; }
  .timeline::before { left: 0; }
}