:root {
  --main-font: 'Open Sans', sans-serif;
  --primary-color: #0082c6;
  --primary-hover: #0082c6;
  --text-color: #333333;
  --subtle-text-color: #555555;
  --intro-color: #444444;
  --button-text: #ffffff;
  --background-color: #f9fafb;
  --card-background: #ffffff;
  --shadow-color: rgba(0, 0, 0, 0.1);
  --border-radius: 8px;
  --transition: all 0.3s ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --text-color: #e0e0e0;
    --subtle-text-color: #cccccc;
    --intro-color: #dddddd;
    --background-color: #121212;
    --card-background: #1e1e1e;
    --shadow-color: rgba(0, 0, 0, 0.6);
    --button-text: #ffffff;
  }
}

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

body {
  font-family: var(--main-font);
  color: var(--text-color);
  background-color: var(--background-color);
  line-height: 1.6;
  transition: var(--transition);
}

a {
  color: #000;
  text-decoration: none;
  transition: var(--transition);
}

a:hover, .content-intro>a:hover {
  color: var(--primary-hover);
}

@media (prefers-color-scheme: dark) {
  a {
    color: #0082c6;
  }
  a:hover, .content-intro>a:hover {
    color: #fff;
  }
  .content-intro>a {
    color: var(--primary-color);
  }
}

#content {
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  padding: 24px 16px;
}

.content-container {
  margin: 0 auto;
  padding: 0 16px 32px;
}

.center-text {
  text-align: center;
}

.conference-header {
  border-left: 6px solid var(--primary-color);
  padding: 24px;
  border-radius: var(--border-radius);
  margin-bottom: 32px;
  box-shadow: 0 2px 10px var(--shadow-color);
  background-color: var(--card-background);
}

.conference-header h1 {
  font-size: 28px;
  margin-bottom: 16px;
  color: var(--primary-color);
  line-height: 1.4;
}

.conference-header p {
  margin-bottom: 8px;
  font-size: 16px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.conference-header p:nth-of-type(1)::before {
  content: "📌";
}
.conference-header p:nth-of-type(2)::before {
  content: "🗓️";
}
.conference-header p:nth-of-type(3)::before {
  content: "🏛️";
}
.conference-header p:nth-of-type(4)::before {
  content: "👥";
}

.content-box {
  padding: 1.5rem;
  border-radius: var(--border-radius);
  box-shadow: 0 2px 8px var(--shadow-color);
  margin: 1rem 0;
}

.content-odd {
  background: var(--card-background);
}

.content-even {
  background: linear-gradient(135deg, rgba(0, 130, 198, 0.05), rgba(0, 0, 0, 0.05));
}

.content-box h2 {
  font-size: 1.75rem;
  font-weight: 600;
  color: var(--primary-color);
  border-bottom: 2px solid var(--primary-color);
  padding-bottom: 0.5rem;
  margin-bottom: 1rem;
  width: auto;
}

.content-box p {
  font-size: 1rem;
  color: var(--intro-color);
  text-align: justify;
}

.content-box ul {
  padding-left: 1.5rem;
  list-style: none;
}

.content-box ul li {
  position: relative;
  margin-bottom: 0.75rem;
  padding-left: 1.5rem;
  color: var(--intro-color);
}

.content-box ul li::before {
  content: "\2022";
  position: absolute;
  left: 0;
  color: var(--primary-color);
  font-size: 1.2rem;
}

.org-content-container {
  padding: 1.5rem;
  border-radius: var(--border-radius);
  background: var(--card-background);
  box-shadow: 0 2px 8px var(--shadow-color);
}

.org-organizer {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  align-items: center;
}

.org-organizer-intro {
  flex: 1;
  min-width: 250px;
  font-size: 1rem;
  color: var(--intro-color);
  text-align: justify;
}

.org-logo-wrapper {
  flex: 0 0 auto;
}

.org-logo {
  max-width: 150px;
  height: auto;
  border-radius: 4px;
  transition: transform 0.3s ease;
}

.org-logo:hover {
  transform: scale(1.05);
}

.keynote-card {
  padding: 1.5rem;
  transition: transform 0.3s ease;
}

.keynote-card:hover {
  transform: translateY(-4px);
}

.keynote-card h2 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--primary-color);
  margin-bottom: 0.75rem;
}

.keynote-card p {
  font-size: 1rem;
  color: var(--subtle-text-color);
  margin-bottom: 0.5rem;
}

.keynote-card ul {
  padding-left: 1.5rem;
}

.keynote-card ul li {
  margin-bottom: 0.5rem;
  color: var(--intro-color);
}

.keynote-info {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

.keynote-left,
.keynote-right {
  flex: 1 1 300px;
}

.cfp-container {
  padding: 1.5rem;
}

.cfp-name {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--primary-color);
  margin-bottom: 0.75rem;
}

.cfp-details {
  padding-left: 1.5rem;
  list-style: none;
}

.cfp-detail {
  position: relative;
  margin-bottom: 0.5rem;
  padding-left: 1.5rem;
  color: var(--intro-color);
}

.cfp-detail::before {
  content: "\2192";
  position: absolute;
  left: 0;
  color: var(--primary-color);
}

.submit-button {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  background: var(--primary-color);
  color: var(--button-text);
  font-size: 1.25rem;
  font-weight: 600;
  border-radius: var(--border-radius);
  box-shadow: 0 4px 8px var(--shadow-color);
  transition: var(--transition);
  text-align: center;
}

.submit-button:hover {
  background: var(--primary-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 12px var(--shadow-color);
}

.submit-button:active {
  transform: translateY(0);
  box-shadow: 0 2px 4px var(--shadow-color);
}
/* Ẩn phần chi tiết CFP mặc định */
.toggle-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease, opacity 0.4s ease;
  opacity: 0;
  pointer-events: none;
}

/* Khi mở: hiện phần chi tiết */
.toggle-container.open .toggle-content {
  max-height: 1000px; /* đủ lớn để hiển thị tất cả */
  opacity: 1;
  pointer-events: auto;
}
.toggle-header {
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.toggle-arrow {
  transition: transform 0.3s ease;
}

.toggle-container.open .toggle-arrow {
  transform: rotate(180deg);
}
.content-box {
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.content-box:hover {
  transform: translateY(-4px) scale(1.01);
  box-shadow: 0 6px 16px var(--shadow-color);
}
.content-box:hover {
  transform: scale(1.02);
}
.second-title {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--primary-color);
  width: fit-content;
  margin-bottom: 16px;
  border-bottom: 2px solid var(--primary-color);
}
.cfp-section-title {
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--primary-color);
  padding-bottom: 0.5rem;
  margin-bottom: 1rem;
}

.cfp-name {
  font-size: 1.1rem; 
  font-weight: 500; 
  color: var(--primary-color);
  margin-bottom: 0.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  border-bottom: 1px solid var(--primary-color);
}
.contact-container {
  display: flex;
  flex-wrap: wrap;
  gap: 2rem;
  margin-top: 1rem;
}

.contact-left,
.contact-right {
  flex: 1 1 300px;
}

.contact-link {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--primary-color);
  text-decoration: none;
  font-size: 1rem;
  margin-bottom: 1rem;
}

.contact-link:hover {
  color: var(--primary-hover);
  text-decoration: underline;
}

.contact-right iframe {
  border: 0;
  border-radius: var(--border-radius);
  width: 100%;
  height: 250px;
}

@media screen and (max-width: 768px) {
  .conference-header {
    padding: 1.5rem;
  }
  .conference-header h1 {
    font-size: 22px;
  }
  .conference-header p {
    font-size: 15px;
  }
  .content-box h2 {
    font-size: 1.5rem;
  }
  .content-box p,
  .keynote-card p,
  .cfp-container p {
    font-size: 0.95rem;
  }
  .org-logo {
    max-width: 120px;
  }
  .submit-button {
    font-size: 1.1rem;
    padding: 0.6rem 1.2rem;
  }
  .keynote-card h2,
  .cfp-name {
    font-size: 1.3rem;
  }
}

@media screen and (max-width: 480px) {
  #content {
    padding: 16px 12px;
  }
  .conference-header h1 {
    font-size: 20px;
  }
  .content-box h2 {
    font-size: 1.3rem;
  }
  .org-organizer {
    flex-direction: column;
    align-items: center;
  }
  .org-logo {
    max-width: 100px;
  }
}