:root {
  --bg-color: #fafafa;
  --surface: #ffffff;
  --text-main: #111827;
  --text-muted: #6b7280;
  --primary: #65a30d; /* Minimal green accent */
  --border-color: #e5e7eb;
  --section-bg-alt: #f3f4f6; /* 연한 회색 배경 (구분용) */
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family:
    "Pretendard Variable",
    -apple-system,
    sans-serif;
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  word-break: keep-all;
  overflow-wrap: break-word;
}

/* Navigation */
nav {
  position: sticky;
  top: 0;
  padding: 24px 5%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: rgba(250, 250, 250, 0.9);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  z-index: 100;
}

.logo {
  font-size: 20px;
  font-weight: 800;
  color: var(--text-main);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.logo span {
  color: var(--primary);
}

.nav-links {
  display: flex;
  align-items: flex-start;
  gap: 40px;
}

.nav-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 15px;
  font-weight: 500;
  transition: color 0.2s;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

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

/* Common Section Styles */
section {
  padding: 120px 24px;
}

.section-header {
  max-width: 1000px;
  margin: 0 auto 60px;
}

.section-label {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--primary);
  font-weight: 600;
  margin-bottom: 16px;
  display: block;
}

.section-title {
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-main);
}

/* Home Section */
#home {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding-top: 60px;
  background:
    linear-gradient(rgba(250, 250, 250, 0.75), rgba(250, 250, 250, 1)),
    url("assets/images/zcell-station.png") center/cover no-repeat;
}

#home h1 {
  font-size: 56px;
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1.1;
  margin-bottom: 24px;
  color: var(--text-main);
}

#home p {
  font-size: 18px;
  color: var(--text-muted);
  max-width: 600px;
  margin: 0 auto 40px;
}

.cta-btn {
  display: inline-block;
  padding: 14px 32px;
  background: var(--text-main);
  color: #ffffff;
  text-decoration: none;
  border-radius: 6px;
  font-weight: 500;
  font-size: 15px;
  transition: background 0.2s;
}

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

/* About Section */
#about {
  background-color: var(--surface);
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
}

.about-description {
  max-width: 800px;
  font-size: 18px;
  color: var(--text-muted);
  margin-bottom: 60px;
  line-height: 1.8;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 32px;
  max-width: 1000px;
  margin: 0 auto;
}

.article-card {
  background: var(--surface);
  padding: 32px;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  transition:
    transform 0.2s ease,
    box-shadow 0.2s ease;
}

.article-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.04);
  border-color: #d1d5db;
}

.article-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.article-card p {
  font-size: 15px;
  color: var(--text-muted);
}

/* Members Section — no card boxing. Content sits directly on the section
   with a bigger photo and generous whitespace between people, instead of
   being squeezed into a small contained box. */
#members {
  background-color: var(--surface);
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
}

#members .grid {
  /* Same centered 1000px box as .section-header, so this shares its left
       edge with "Members" regardless of viewport width — the card
       itself (not the grid) is what caps the readable width. */
  grid-template-columns: 1fr;
  max-width: 1000px;
  margin: 0 auto;
  gap: 56px;
}

.member-card {
  display: flex;
  align-items: center;
  gap: 32px;
  max-width: 640px;
  text-align: left;
}

.member-photo {
  flex-shrink: 0;
  width: 140px;
  height: 140px;
  border-radius: 50%;
  background: var(--section-bg-alt);
  border: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
}

.member-photo svg {
  width: 64px;
  height: 64px;
}

.member-info {
  flex: 1;
  min-width: 0;
}

.member-photo img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 50%;
}

.member-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 6px;
  letter-spacing: -0.02em;
}

.member-card p {
  font-size: 15px;
  color: var(--text-muted);
}

.member-card .member-major {
  font-size: 13px;
  margin-top: 4px;
}

.member-email {
  display: inline-block;
  margin-top: 12px;
  font-size: 13px;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s;
}

.member-email:hover {
  color: var(--primary);
}

@media (max-width: 640px) {
  .member-card {
    flex-direction: column;
    text-align: center;
    gap: 20px;
  }

  .member-photo {
    width: 140px;
    height: 140px;
  }
}

/* Contact Section */
#contact {
  background-color: var(--section-bg-alt);
  text-align: center;
}

.contact-card {
  max-width: 600px;
  margin: 0 auto;
  background: var(--surface);
  padding: 60px 40px;
  border-radius: 16px;
  border: 1px solid var(--border-color);
}

.contact-card h3 {
  font-size: 24px;
  margin-bottom: 16px;
}

.contact-card p {
  color: var(--text-muted);
  margin-bottom: 32px;
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
  margin-bottom: 32px;
  text-align: left;
}

.contact-form input[type="text"],
.contact-form input[type="email"],
.contact-form textarea {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background: var(--bg-color);
  color: var(--text-main);
  font-family: inherit;
  font-size: 15px;
  transition: border-color 0.2s;
}

.contact-form input[type="text"]:focus,
.contact-form input[type="email"]:focus,
.contact-form textarea:focus {
  outline: none;
  border-color: var(--primary);
}

.contact-form textarea {
  resize: vertical;
  min-height: 120px;
}

.contact-form button {
  align-self: center;
  border: none;
  cursor: pointer;
}

/* Honeypot spam trap — kept in the tab/DOM flow (not display:none) so bots
   that skip hidden fields still fill it in, but invisible to real users. */
.hp-field {
  position: absolute;
  left: -9999px;
  width: 1px;
  height: 1px;
  opacity: 0;
}

.email-link {
  font-size: 20px;
  font-weight: 600;
  color: var(--primary);
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: border-color 0.2s;
}

.email-link:hover {
  border-color: var(--primary);
}

.office-address {
  margin-top: 16px;
  font-size: 13px;
  color: var(--text-muted);
}

/* Footer */
footer {
  background-color: var(--bg-color);
  margin-top: 80px;
  padding: 40px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  border-top: 1px solid var(--border-color);
}

.footer-text {
  flex: 1;
  min-width: 0;
  color: var(--text-muted);
  font-size: 13px;
  text-align: left;
}

footer .lang-slider {
  margin-top: 0;
  margin-left: auto;
}

@media (max-width: 768px) {
  #home h1 {
    font-size: 36px;
  }
  .nav-links {
    display: none;
    position: absolute;
    top: 85px;
    left: 0;
    right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    align-items: center;
    padding: 20px 0;
    gap: 20px;
  }
  .nav-links.active {
    display: flex;
  }
  .hamburger-menu {
    display: block;
  }
  section {
    padding: 80px 24px;
  }
}

/* ===== Language Switch (pure HTML — links to a sibling *.ko.html page) ===== */
.lang-slider {
  position: relative;
  display: inline-flex;
  flex: none;
  align-items: center;
  width: 88px;
  height: 34px;
  padding: 4px;
  border: 1px solid var(--border-color);
  border-radius: 999px;
  background: var(--section-bg-alt);
  text-decoration: none;
  user-select: none;
  transition:
    border-color 0.2s,
    box-shadow 0.2s;
  z-index: 120;
}

.lang-slider:hover {
  border-color: #c4d9a8;
  box-shadow: 0 0 0 4px rgba(101, 163, 13, 0.08);
}

.lang-slider span {
  position: relative;
  z-index: 2;
  flex: 1;
  text-align: center;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  transition: color 0.25s ease;
}

/* KOR on the left, EN on the right */
.lang-slider-ko {
  order: 1;
}
.lang-slider-en {
  order: 2;
}

.lang-slider::before {
  content: "";
  position: absolute;
  top: 4px;
  left: 4px;
  width: calc(50% - 4px);
  height: calc(100% - 8px);
  background: linear-gradient(135deg, #7cb518, var(--primary));
  border-radius: 999px;
  box-shadow: 0 2px 6px rgba(101, 163, 13, 0.4);
  transition: transform 0.3s cubic-bezier(0.65, 0, 0.35, 1);
  z-index: 1;
}

/* On a Korean page: thumb sits on KOR (left, default position) */
.lang-slider.is-ko .lang-slider-ko {
  color: #ffffff;
}

/* On an English page: thumb slides to EN (right) */
.lang-slider.is-en::before {
  transform: translateX(100%);
}

.lang-slider.is-en .lang-slider-en {
  color: #ffffff;
}

/* Negative letter-spacing tightens Latin type nicely but crowds Hangul,
   which is already full-width and evenly spaced — undo it on Korean pages
   only, so the English headings keep their tighter tracking. */
:lang(ko) #home h1,
:lang(ko) .section-title,
:lang(ko) .article-card h3,
:lang(ko) .member-card h3 {
  letter-spacing: normal;
}

/* Hamburger Menu */
.hamburger-menu {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
  z-index: 101;
}

.hamburger-line {
  display: block;
  width: 25px;
  height: 3px;
  background-color: var(--text-main);
  margin: 5px 0;
  transition: all 0.3s ease-in-out;
}

@media (max-width: 768px) {
  .hamburger-menu {
    display: block;
  }

  .lang-slider {
    width: 84px;
    height: 32px;
    margin: 0 auto;
  }
}