* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scrollbar-gutter: stable;
}

/* ===== 라이트 ===== */
body {
  margin: 0;
  padding-top: 80px;
  background: #f5f7fa;
  color: #111;
  font-family: Arial, sans-serif;
  transition: background 0.25s ease, color 0.25s ease;
}

/* ===== 다크 ===== */
body.dark {
  background: #0d1117;
  color: #c9d1d9;
}

/* ===== NAV ===== */
nav {
  position: fixed;
  top: 0;
  width: 100%;
  padding: 16px 40px;
  display: flex;
  align-items: center;
  background: #ffffff;
  z-index: 1000;
  transition: background 0.25s ease;
}

body.dark nav {
  background: #0b0f14;
}

.logo {
  font-weight: bold;
  font-size: 18px;
}

.menu {
  display: flex;
  gap: 24px;
  margin-left: 40px;
}

nav a {
  color: inherit;
  text-decoration: none;
  font-weight: 500;
}

/* ===== 버튼 (심플 & 세련) ===== */
.links {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 10px;
}

.toggle-btn {
  padding: 6px 14px;
  border-radius: 999px;
  border: 1px solid currentColor;
  background: transparent;
  color: inherit;
  font-size: 13px;
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease;
}

.toggle-btn:hover {
  background: rgba(0,0,0,0.08);
}

body.dark .toggle-btn:hover {
  background: rgba(255,255,255,0.1);
}

/* ===== 아이콘 ===== */
.icon {
  width: 32px;
  height: 32px;
  object-fit: contain;
  transition: transform 0.2s ease;
}

.icon:hover {
  transform: scale(1.15);
}

/* ===== 섹션 ===== */
section {
  padding: 100px 30px;
  max-width: 900px;
  margin: auto;
}

.hero {
  text-align: center;
  padding-top: 120px;
}

/* ===== 카드 ===== */
.cards {
  display: flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

.card {
  background: #ffffff;
  color: #111;
  border-radius: 12px;
  padding: 20px;
  width: 220px;
  text-align: center;
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

body.dark .card {
  background: #161b22;
  color: #c9d1d9;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.25);
}