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

/* ── Theme variables ── */
[data-theme="dark"] {
  --bg: #0a0a0a;
  --surface: #111111;
  --border: #1f1f1f;
  --text: #e8e8e8;
  --muted: #999;
  --accent: #6366f1;
  --accent-hover: #4f52e0;
  --nav-bg: rgba(10, 10, 10, 0.85);
  --card-hover-border: #333;
  --btn-ghost-hover-border: #444;
  --dot-color: rgba(255, 255, 255, 0.055);
  --glow-color: rgba(99, 102, 241, 0.14);
}

[data-theme="light"] {
  --bg: #ffffff;
  --surface: #f5f5f5;
  --border: #e5e5e5;
  --text: #0d0d0d;
  --muted: #555;
  --accent: #6366f1;
  --accent-hover: #4f52e0;
  --nav-bg: rgba(255, 255, 255, 0.85);
  --card-hover-border: #ccc;
  --btn-ghost-hover-border: #bbb;
  --dot-color: rgba(0, 0, 0, 0.055);
  --glow-color: rgba(99, 102, 241, 0.08);
}

:root {
  --font: 'Inter', system-ui, -apple-system, sans-serif;
}

html {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  transition: background 0.2s ease, color 0.2s ease;
}

body {
  min-height: 100vh;
  line-height: 1.6;
  background-image: radial-gradient(circle, var(--dot-color) 1px, transparent 1px);
  background-size: 28px 28px;
}

/* ── Hero glow ── */
.hero {
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -120px;
  left: 50%;
  transform: translateX(-50%);
  width: 700px;
  height: 500px;
  background: radial-gradient(ellipse at center, var(--glow-color) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

.hero > * {
  position: relative;
  z-index: 1;
}

a {
  color: inherit;
  text-decoration: none;
}

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

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 500;
  line-height: 1;
  cursor: pointer;
  border: none;
  transition: all 0.15s ease;
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-hover);
}

.btn-ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-ghost:hover {
  border-color: var(--btn-ghost-hover-border);
  background: var(--surface);
}

/* ── Nav ── */
nav {
  border-bottom: 1px solid var(--border);
  padding: 16px 0;
  position: sticky;
  top: 0;
  background: var(--nav-bg);
  backdrop-filter: blur(12px);
  z-index: 100;
  transition: background 0.2s ease, border-color 0.2s ease;
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.nav-logo {
  display: flex;
  align-items: center;
  line-height: 0;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  color: var(--muted);
  font-size: 0.9rem;
  transition: color 0.15s;
}

.nav-links a.btn {
  color: #fff;
}

.nav-links a:hover {
  color: var(--text);
}

/* ── Nav right cluster (toggle + hamburger) ── */
.nav-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

/* ── Theme toggle ── */
.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--muted);
  transition: border-color 0.15s, color 0.15s;
  flex-shrink: 0;
}

.theme-toggle:hover {
  border-color: var(--btn-ghost-hover-border);
  color: var(--text);
}

.theme-toggle svg {
  width: 16px;
  height: 16px;
}

/* Show sun in dark mode (click = go light), moon in light mode (click = go dark) */
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="dark"] .icon-sun  { display: block; }
[data-theme="light"] .icon-sun  { display: none; }
[data-theme="light"] .icon-moon { display: block; }

/* ── Logo variants ── */
[data-theme="dark"]  .logo-for-light { display: none; }
[data-theme="dark"]  .logo-for-dark  { display: block; }
[data-theme="light"] .logo-for-dark  { display: none; }
[data-theme="light"] .logo-for-light { display: block; }

/* ── Hamburger ── */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
}

/* ── Drawer ── */
.drawer-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  opacity: 0;
  transition: opacity 0.25s ease;
}

.drawer-overlay.open {
  display: block;
  opacity: 1;
}

.drawer {
  position: fixed;
  top: 0;
  right: 0;
  height: 100%;
  width: 280px;
  background: var(--bg);
  border-left: 1px solid var(--border);
  z-index: 201;
  transform: translateX(100%);
  transition: transform 0.25s ease;
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 32px;
}

.drawer.open {
  transform: translateX(0);
}

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.drawer-close {
  background: none;
  border: none;
  color: var(--muted);
  font-size: 1.1rem;
  cursor: pointer;
  padding: 4px;
  line-height: 1;
}

.drawer-close:hover {
  color: var(--text);
}

.drawer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.drawer-links a {
  display: block;
  padding: 10px 0;
  color: var(--muted);
  font-size: 1rem;
  border-bottom: 1px solid var(--border);
  transition: color 0.15s;
}

.drawer-links a:hover {
  color: var(--text);
}

.drawer-links li:last-child a {
  border-bottom: none;
  margin-top: 8px;
  color: #fff;
}

@media (max-width: 640px) {
  .nav-links { display: none; }
  .hamburger { display: flex; }
}

/* ── Footer ── */
footer {
  border-top: 1px solid var(--border);
  padding: 40px 0;
  margin-top: 80px;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.footer-links {
  display: flex;
  gap: 24px;
  list-style: none;
}

.footer-links a {
  color: var(--muted);
  font-size: 0.875rem;
  transition: color 0.15s;
}

.footer-links a:hover {
  color: var(--text);
}

.footer-copy {
  color: var(--muted);
  font-size: 0.8rem;
  width: 100%;
  margin-top: 16px;
}

/* ── Sections ── */
section {
  padding: 80px 0;
}

.section-label {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}

h1, h2, h3 {
  letter-spacing: -0.03em;
  line-height: 1.2;
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); }
h3 { font-size: 1.1rem; }

.text-muted { color: var(--muted); }

/* ── Cards ── */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 28px;
  transition: border-color 0.2s, background 0.2s;
}

.card:hover {
  border-color: var(--card-hover-border);
}

.card-problem { border-color: rgba(224, 85, 85, 0.35); }
.card-solution { border-color: rgba(85, 224, 122, 0.35); }