/* =========================================================
   Portfolio – Ariansyah (Data & Applied Math)
   ========================================================= */

/* ── Custom properties ─────────────────────────────────── */
:root {
  --bg:          #0d1117;
  --bg-alt:      #161b22;
  --surface:     #21262d;
  --border:      #30363d;
  --text:        #e6edf3;
  --text-muted:  #8b949e;
  --accent:      #58a6ff;
  --accent-dim:  #1f3a5f;
  --accent2:     #79c0ff;
  --success:     #3fb950;
  --radius:      0.75rem;
  --shadow:      0 4px 24px rgba(0,0,0,.5);
  --nav-h:       64px;
  --transition:  0.25s ease;
}

/* ── Reset / Base ──────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; font-size: 16px; }

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  line-height: 1.7;
  overflow-x: hidden;
}

img, svg { display: block; max-width: 100%; }

a { color: var(--accent); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--accent2); }

h1, h2, h3 { line-height: 1.2; }

ul { list-style: none; }

/* ── Utility: container ────────────────────────────────── */
.container {
  width: min(1100px, 92%);
  margin-inline: auto;
}

/* ── Section titles ────────────────────────────────────── */
.section-title {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 700;
  text-align: center;
  margin-bottom: 3rem;
  letter-spacing: -0.03em;
}
.section-title span { color: var(--accent); }

/* ── Buttons ───────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.65rem 1.5rem;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  border: 2px solid transparent;
}
.btn-primary {
  background: var(--accent);
  color: #0d1117;
}
.btn-primary:hover {
  background: var(--accent2);
  color: #0d1117;
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(88,166,255,.35);
}
.btn-outline {
  border-color: var(--accent);
  color: var(--accent);
  background: transparent;
}
.btn-outline:hover {
  background: var(--accent-dim);
  color: var(--accent2);
  transform: translateY(-2px);
}
.btn-full { width: 100%; justify-content: center; }

/* ── Alt background sections ───────────────────────────── */
.alt-bg { background-color: var(--bg-alt); }

/* ── Scroll-reveal animation ────────────────────────────── */
.reveal {
  opacity: 0;
  transform: translateY(36px);
  transition: opacity 0.65s ease, transform 0.65s ease;
}
.reveal.visible {
  opacity: 1;
  transform: none;
}

/* ═══════════════════════════════════════════════════════════
   NAV
═══════════════════════════════════════════════════════════ */
#navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-h);
  z-index: 1000;
  transition: background var(--transition), box-shadow var(--transition);
}
#navbar.scrolled {
  background: rgba(13,17,23,.9);
  backdrop-filter: blur(10px);
  box-shadow: 0 1px 0 var(--border);
}

.nav-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: min(1100px, 92%);
  margin-inline: auto;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
}
.logo-bracket { color: var(--accent); }

nav ul {
  display: flex;
  gap: 2rem;
}
nav a {
  color: var(--text-muted);
  font-weight: 500;
  font-size: 0.9rem;
  letter-spacing: 0.02em;
  position: relative;
  padding-bottom: 4px;
}
nav a::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0;
  width: 0; height: 2px;
  background: var(--accent);
  transition: width var(--transition);
}
nav a:hover, nav a.active { color: var(--text); }
nav a:hover::after, nav a.active::after { width: 100%; }

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  transition: all var(--transition);
  border-radius: 2px;
}
.hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.hamburger.open span:nth-child(2) { opacity: 0; }
.hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ═══════════════════════════════════════════════════════════
   HERO
═══════════════════════════════════════════════════════════ */
#hero {
  position: relative;
  min-height: 100svh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: calc(var(--nav-h) + 2rem) 1rem 2rem;
  overflow: hidden;
}

#hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.35;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 760px;
}

.hero-greeting {
  font-size: 1.1rem;
  color: var(--accent);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.hero-name {
  font-size: clamp(3rem, 8vw, 5.5rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  background: linear-gradient(135deg, var(--text) 40%, var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5rem;
}

.hero-title {
  font-size: clamp(1.1rem, 3vw, 1.6rem);
  font-weight: 400;
  color: var(--text-muted);
  min-height: 2em;
  margin-bottom: 1.2rem;
}
.cursor {
  display: inline-block;
  animation: blink 0.8s step-end infinite;
  color: var(--accent);
  margin-left: 1px;
}
@keyframes blink { 0%,100%{opacity:1} 50%{opacity:0} }

.hero-blurb {
  font-size: 1.05rem;
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.hero-cta { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }

.scroll-hint {
  position: absolute;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
  color: var(--text-muted);
  animation: bounce 2s infinite;
}
@keyframes bounce {
  0%,100%{transform:translateX(-50%) translateY(0)}
  50%{transform:translateX(-50%) translateY(8px)}
}

/* ═══════════════════════════════════════════════════════════
   ABOUT
═══════════════════════════════════════════════════════════ */
#about { padding: 6rem 0; }

.about-grid {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 3rem;
  align-items: center;
}

.avatar-placeholder {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  background: var(--accent-dim);
  border: 3px solid var(--accent);
  overflow: hidden;
  margin: 0 auto;
}
.avatar-placeholder svg {
  width: 100%;
  height: 100%;
}

.about-text p { color: var(--text-muted); margin-bottom: 1rem; }
.about-text p strong { color: var(--text); }

/* ═══════════════════════════════════════════════════════════
   SKILLS
═══════════════════════════════════════════════════════════ */
#skills { padding: 6rem 0; }

.skill-categories {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2.5rem;
}

.skill-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.skill-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow);
  border-color: var(--accent);
}

.skill-icon {
  width: 44px;
  height: 44px;
  background: var(--accent-dim);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1rem;
}
.skill-icon svg {
  width: 24px;
  height: 24px;
  stroke: var(--accent);
}

.skill-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.75rem;
}

.skill-card ul li {
  font-size: 0.875rem;
  color: var(--text-muted);
  padding: 0.2rem 0;
  border-bottom: 1px solid var(--border);
}
.skill-card ul li:last-child { border-bottom: none; }

/* Badge row */
.badge-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  justify-content: center;
}

.badge {
  padding: 0.3rem 0.85rem;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--accent-dim);
  color: var(--accent);
  border: 1px solid var(--accent);
  letter-spacing: 0.03em;
}

/* ═══════════════════════════════════════════════════════════
   PROJECTS
═══════════════════════════════════════════════════════════ */
#projects { padding: 6rem 0; }

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
}

.project-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.project-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow);
  border-color: var(--accent);
}

.project-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

.project-icon { font-size: 2rem; }

.project-links {
  display: flex;
  gap: 0.75rem;
}
.project-links a {
  color: var(--text-muted);
  transition: color var(--transition);
}
.project-links a:hover { color: var(--accent); }

.project-card h3 {
  font-size: 1rem;
  font-weight: 600;
}

.project-card p {
  font-size: 0.875rem;
  color: var(--text-muted);
  flex: 1;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: auto;
}
.project-tags span {
  font-size: 0.75rem;
  color: var(--accent);
  background: var(--accent-dim);
  border-radius: 4px;
  padding: 0.15rem 0.5rem;
  font-weight: 500;
}

/* ═══════════════════════════════════════════════════════════
   EDUCATION / TIMELINE
═══════════════════════════════════════════════════════════ */
#education { padding: 6rem 0; }

.timeline {
  position: relative;
  max-width: 760px;
  margin-inline: auto;
}
.timeline::before {
  content: '';
  position: absolute;
  left: 16px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--border);
}

.timeline-item {
  position: relative;
  padding-left: 52px;
  margin-bottom: 2.5rem;
}
.timeline-item:last-child { margin-bottom: 0; }

.timeline-dot {
  position: absolute;
  left: 8px;
  top: 6px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--bg-alt);
  z-index: 1;
}

.timeline-content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
}

.timeline-date {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.timeline-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 0.2rem;
}

.timeline-org {
  font-size: 0.875rem;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.timeline-content p:last-child {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* ═══════════════════════════════════════════════════════════
   CONTACT
═══════════════════════════════════════════════════════════ */
#contact { padding: 6rem 0; }

.contact-lead {
  text-align: center;
  color: var(--text-muted);
  max-width: 560px;
  margin: -2rem auto 3rem;
}

.contact-wrapper {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 3rem;
  align-items: start;
  max-width: 860px;
  margin-inline: auto;
}

/* Form */
.form-group { margin-bottom: 1.25rem; }

.form-group label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--text-muted);
}

.form-group input,
.form-group textarea {
  width: 100%;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.7rem 1rem;
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
  transition: border-color var(--transition), box-shadow var(--transition);
  resize: vertical;
}
.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(88,166,255,.15);
}
.form-group input::placeholder,
.form-group textarea::placeholder { color: var(--text-muted); }

.form-error {
  display: block;
  font-size: 0.8rem;
  color: #f85149;
  margin-top: 0.3rem;
  min-height: 1.1em;
}

.form-success {
  text-align: center;
  color: var(--success);
  margin-top: 0.75rem;
  font-weight: 600;
}

/* Contact side links */
.contact-links {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  padding-top: 0.25rem;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  color: var(--text-muted);
  font-size: 0.9rem;
  transition: color var(--transition);
}
.contact-item:hover { color: var(--accent); }
.contact-item svg { flex-shrink: 0; }

/* ═══════════════════════════════════════════════════════════
   FOOTER
═══════════════════════════════════════════════════════════ */
footer {
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  text-align: center;
  padding: 2rem 1rem;
}

footer p {
  font-size: 0.875rem;
  color: var(--text-muted);
}
footer a { color: var(--accent); }

.footer-math {
  font-family: 'Georgia', serif;
  font-style: italic;
  margin-top: 0.5rem;
  color: var(--border);
  font-size: 0.85rem;
}

/* ═══════════════════════════════════════════════════════════
   RESPONSIVE
═══════════════════════════════════════════════════════════ */
@media (max-width: 768px) {
  /* Mobile nav */
  .hamburger { display: flex; }

  nav {
    position: fixed;
    top: var(--nav-h);
    left: 0; right: 0;
    background: var(--bg-alt);
    border-bottom: 1px solid var(--border);
    transform: translateY(-110%);
    transition: transform var(--transition);
    padding: 1rem 0;
  }
  nav.open { transform: none; }

  nav ul {
    flex-direction: column;
    align-items: center;
    gap: 1rem;
  }
  nav a { font-size: 1rem; }

  /* About */
  .about-grid { grid-template-columns: 1fr; text-align: center; }
  .avatar-placeholder { margin: 0 auto 1rem; }

  /* Contact */
  .contact-wrapper { grid-template-columns: 1fr; }
  .contact-links { padding-top: 0; }
}

@media (max-width: 480px) {
  .hero-cta { flex-direction: column; align-items: center; }
  .hero-cta .btn { width: 100%; max-width: 260px; justify-content: center; }
}