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

html, body {
  height: 100%;
  font-family: 'Noto Sans KR', sans-serif;
}
body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
body.dark {
  background: #121212;
  color: #e5e5e5;
}

a { text-decoration: none; }
ul { list-style: none; }

/* header */
header {
  width: 100%;
  min-height: 150px;
  height: 150px;
  padding: 32px 0 20px 0;
  text-align: center;
  font-size: 1.5rem;
  letter-spacing: 1px;
}
header a {
  font-size: 30px;
  font-weight: bold;
  color: #121212;
}
body.dark header a {
  color: #f3f4f6;
}

/* nav */
nav {
  background: #fff;
  box-shadow: 0 2px 10px rgba(0,0,0,0.08);
  position: sticky;
  top: 0;
  z-index: 100;
}
body.dark nav {
  background: #1f2937;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.6);
}

nav ul {
  display: flex;
  justify-content: center;
}
nav li {
  padding: 0;
}
nav a {
  display: block;
  padding: 16px 28px;
  color: #343a40;
  font-weight: 500;
  font-size: 1.08rem;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-bottom 0.2s;
}
body.dark nav a {
  color: #d1d5db;
}

nav a:hover, nav a.active {
  color: #2563eb;
  border-bottom: 2.5px solid #2563eb;
}
body.dark nav a:hover,
body.dark nav a.active {
  color: #60a5fa;
  border-bottom: 2.5px solid #60a5fa;
}

/* content */
main {
  flex: 1 0 auto;
  width: 100%;
  position: relative;
}
.container {
  width: 900px;
  margin: 0 auto;
  padding: 24px 20px;
}

.page_message {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
  color: gray;
}

/* footer */
footer {
  position: relative;
  width: 100%;
  min-height: 30px;
  text-align: center;
  padding: 20px 0;
  flex-shrink: 0;
  font-size: 12px;
}
body.dark footer {
  background: #1f2937;
  color: #d1d5db;
}

/* common FAB */
.c-fab {
  position: fixed;
  bottom: 40px;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  border: 1px solid #ddd;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.25);
  font-size: 14px;
  font-weight: bold;
  background-color: #fff;
  transition: background 0.2s, transform 0.2s, box-shadow 0.2s, opacity 0.2s;
  z-index: 1000;
  cursor: pointer;
}
.c-fab:hover {
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.35);
}
body.dark .c-fab {
  border: 1px solid #555;
  background: #333333;
  color: #f9f9f9;
}

#darkModeToggle {
  right: 50px;
}
#scrollTopBtn {
  right: 120px;
  opacity: 0;
  pointer-events: none;
}