:root {
  --primary-color: #FF6B6B;
  --primary-light: #FF8E8E;
  --secondary-color: #4ECDC4;
  --accent-color: #FFE66D;
  --accent-pink: #FF6B9D;
  --accent-purple: #A463FF;
  --text-dark: #2C3E50;
  --text-medium: #5A6C7D;
  --text-light: #8492A6;
  --bg-primary: #FFFFFF;
  --bg-secondary: #F8FAFF;
  --bg-alt: #F0F8FF;
  --border-color: #E2E8F0;
  --shadow-light: 0 2px 4px rgba(0, 0, 0, 0.05);
  --shadow-medium: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-glow: 0 0 20px rgba(255, 107, 107, 0.3);
  --gradient-hero: linear-gradient(135deg, #FF6B6B 0%, #4ECDC4 50%, #FFE66D 100%);
  --gradient-card: linear-gradient(135deg, #FFE66D 0%, #FF6B9D 100%);
  --gradient-button: linear-gradient(135deg, #FF6B6B 0%, #A463FF 100%);
  --gradient-section: linear-gradient(135deg, rgba(255, 230, 109, 0.1) 0%, rgba(164, 99, 255, 0.1) 100%);
}

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

html {
  scroll-behavior: smooth;
}

/* Exciting animations */
@keyframes float {
  0%, 100% { transform: translateY(0px); }
  50% { transform: translateY(-10px); }
}

@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.05); }
  100% { transform: scale(1); }
}

@keyframes rainbow {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

@keyframes slideInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes sparkle {
  0%, 100% { opacity: 0.3; transform: scale(0.8); }
  50% { opacity: 1; transform: scale(1.2); }
}

body {
  font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
  line-height: 1.7;
  color: var(--text-dark);
  background: var(--bg-primary);
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* Hero Section */
.hero {
  background: var(--gradient-hero);
  background-size: 300% 300%;
  animation: rainbow 8s ease infinite;
  color: white;
  text-align: center;
  padding: 6rem 0;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(45deg, transparent 30%, rgba(255, 255, 255, 0.1) 50%, transparent 70%);
  animation: sparkle 3s ease-in-out infinite;
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 1px, transparent 1px);
  background-size: 50px 50px;
  animation: float 6s ease-in-out infinite;
  pointer-events: none;
}

.hero-title {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 700;
  margin-bottom: 1rem;
  animation: pulse 2s ease-in-out infinite;
  text-shadow: 0 0 20px rgba(255, 255, 255, 0.5);
  position: relative;
  z-index: 1;
}

.hero-subtitle {
  font-size: clamp(1rem, 2.5vw, 1.2rem);
  font-weight: 300;
  margin-bottom: 1.5rem;
  opacity: 0.9;
}

.hero-date {
  font-size: 1.2rem;
  font-weight: 500;
  padding: 1rem 2rem;
  background: rgba(255, 255, 255, 0.2);
  backdrop-filter: blur(10px);
  border-radius: 25px;
  border: 1px solid rgba(255, 255, 255, 0.3);
  display: inline-block;
  animation: float 4s ease-in-out infinite;
  box-shadow: var(--shadow-glow);
  position: relative;
  z-index: 1;
  transition: all 0.3s ease;
}

.hero-date:hover {
  transform: scale(1.05);
  box-shadow: 0 0 30px rgba(255, 255, 255, 0.8);
}

/* Navigation */
.nav-bar {
  background: var(--bg-primary);
  box-shadow: var(--shadow-medium);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-menu {
  display: flex;
  list-style: none;
  justify-content: center;
  flex-wrap: wrap;
  padding: 1rem 0;
}

.nav-menu li {
  margin: 0 1rem;
}

.nav-link {
  text-decoration: none;
  color: var(--text-dark);
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: 20px;
  transition: all 0.3s ease;
}

.nav-link:hover {
  background: var(--primary-color);
  color: white;
}

/* Sections */
.section {
  padding: 4rem 0;
  animation: slideInUp 0.8s ease-out;
}

.alt-bg {
  background: var(--gradient-section);
  position: relative;
}

.alt-bg::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: radial-gradient(circle at 25% 25%, rgba(255, 107, 107, 0.1) 0%, transparent 50%),
                    radial-gradient(circle at 75% 75%, rgba(78, 205, 196, 0.1) 0%, transparent 50%);
  animation: float 8s ease-in-out infinite;
  pointer-events: none;
}

.section-header {
  text-align: center;
  margin-bottom: 3rem;
}

.section-title {
  font-size: clamp(2rem, 3.5vw, 3rem);
  font-weight: 700;
  color: var(--text-dark);
  position: relative;
  display: inline-block;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--gradient-button);
  border-radius: 2px;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.6s ease;
}

.section:hover .section-title::after {
  transform: scaleX(1);
}

/* Overview Section */
.overview-content {
  max-width: 800px;
  margin: 0 auto;
  text-align: center;
}

.overview-content p {
  font-size: 1.1rem;
  margin-bottom: 1.5rem;
  color: var(--text-medium);
}

.important-notes {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 2rem;
}

.note-item {
  background: var(--bg-primary);
  padding: 1.5rem;
  border-radius: 15px;
  box-shadow: var(--shadow-light);
  border-left: 4px solid var(--primary-color);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.note-item::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--gradient-card);
  opacity: 0;
  transition: opacity 0.3s ease;
  z-index: 0;
}

.note-item:hover {
  transform: translateY(-5px) scale(1.02);
  box-shadow: var(--shadow-glow);
}

.note-item:hover::before {
  opacity: 0.1;
}

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

/* Date Time Section */
.datetime-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  max-width: 800px;
  margin: 0 auto;
}

.datetime-card, .venue-card {
  background: var(--bg-primary);
  padding: 2rem;
  border-radius: 15px;
  box-shadow: var(--shadow-medium);
}

.datetime-card h3, .venue-card h3 {
  font-size: 1.3rem;
  color: var(--primary-color);
  margin-bottom: 1rem;
}

.datetime-info {
  font-size: 1.1rem;
  color: var(--text-dark);
}

.venue-details {
  margin-top: 1.5rem;
}

.online-venue, .offline-venue {
  margin-bottom: 1.5rem;
  padding: 1rem;
  background: var(--bg-secondary);
  border-radius: 8px;
}

.online-venue h4, .offline-venue h4 {
  color: var(--primary-color);
  margin-bottom: 0.5rem;
}

.online-venue a {
  color: var(--primary-color);
  text-decoration: none;
  word-break: break-all;
}

.online-venue a:hover {
  text-decoration: underline;
}

.access-info {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-color);
}

/* Timetable Section */
.timetable-content {
  text-align: center;
}

.timetable-link {
  display: inline-block;
  background: var(--gradient-button);
  color: white;
  text-decoration: none;
  padding: 2rem 3rem;
  border-radius: 25px;
  font-size: 1.3rem;
  font-weight: 600;
  transition: all 0.4s ease;
  margin: 2rem auto;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-glow);
  animation: pulse 3s ease-in-out infinite;
}

.timetable-link::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
  transition: left 0.6s ease;
}

.timetable-link:hover::before {
  left: 100%;
}

.timetable-link:hover {
  transform: translateY(-8px) scale(1.05);
  box-shadow: 0 10px 30px rgba(255, 107, 107, 0.4);
  animation: none;
}

/* Participation Section */
.participation-content {
  max-width: 700px;
  margin: 0 auto;
}

.participation-content > p {
  text-align: center;
  font-size: 1.1rem;
  margin-bottom: 2rem;
  color: var(--text-medium);
}

.participation-methods {
  display: grid;
  gap: 1rem;
  margin-bottom: 3rem;
}

.method-item {
  display: flex;
  align-items: center;
  background: var(--bg-primary);
  padding: 1.5rem;
  border-radius: 15px;
  box-shadow: var(--shadow-light);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.method-item::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--gradient-section);
  opacity: 0;
  transition: opacity 0.3s ease;
  z-index: 0;
}

.method-item:hover {
  transform: translateX(10px) scale(1.02);
  box-shadow: var(--shadow-medium);
}

.method-item:hover::before {
  opacity: 1;
}

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

.method-icon {
  font-size: 1.5rem;
  margin-right: 1rem;
}

.method-text {
  font-size: 1rem;
  color: var(--text-dark);
}

.method-link {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
}

.method-link:hover {
  text-decoration: underline;
}

.warning-notice {
  background: #fff3cd;
  border: 1px solid #ffeaa7;
  border-radius: 10px;
  padding: 1.5rem;
}

.warning-notice h3 {
  color: #856404;
  margin-bottom: 0.5rem;
}

.warning-notice p {
  color: #856404;
  margin: 0;
}

/* Past Section */
.past-content {
  max-width: 700px;
  margin: 0 auto;
}

.past-section {
  margin-bottom: 3rem;
  text-align: center;
}

.past-section h3 {
  font-size: 1.3rem;
  color: var(--primary-color);
  margin-bottom: 1.5rem;
}

.year-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem;
}

.year-link {
  background: var(--bg-primary);
  color: var(--primary-color);
  text-decoration: none;
  padding: 0.7rem 1.2rem;
  border-radius: 25px;
  border: 2px solid var(--primary-color);
  transition: all 0.4s ease;
  position: relative;
  overflow: hidden;
}

.year-link::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--gradient-button);
  transform: scale(0);
  border-radius: 50%;
  transition: transform 0.4s ease;
  z-index: 0;
}

.year-link span {
  position: relative;
  z-index: 1;
}

.year-link:hover {
  color: white;
  transform: scale(1.1);
  box-shadow: var(--shadow-glow);
}

.year-link:hover::before {
  transform: scale(1.5);
}

.presentation-list-link {
  display: inline-block;
  background: var(--gradient-card);
  color: white;
  text-decoration: none;
  padding: 1.2rem 2.5rem;
  border-radius: 30px;
  font-weight: 600;
  transition: all 0.4s ease;
  box-shadow: var(--shadow-medium);
  position: relative;
  overflow: hidden;
}

.presentation-list-link::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0;
  height: 0;
  background: rgba(255, 255, 255, 0.2);
  border-radius: 50%;
  transition: all 0.6s ease;
  transform: translate(-50%, -50%);
}

.presentation-list-link:hover {
  transform: translateY(-5px) scale(1.05);
  box-shadow: 0 10px 25px rgba(255, 107, 157, 0.4);
}

.presentation-list-link:hover::before {
  width: 300px;
  height: 300px;
}

/* Footer */
.footer {
  background: var(--text-dark);
  color: white;
  padding: 2rem 0;
  text-align: center;
}

#hidden-link {
  color: rgba(255, 255, 255, 0.6);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 300;
  transition: all 0.3s ease;
  cursor: default;
}

#hidden-link:hover {
  color: var(--accent-color);
  cursor: pointer;
  text-shadow: 0 0 5px var(--accent-color);
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    padding: 0 1rem;
  }

  .nav-menu {
    flex-direction: column;
    align-items: center;
  }

  .nav-menu li {
    margin: 0.25rem 0;
  }

  .section {
    padding: 3rem 0;
  }

  .important-notes {
    grid-template-columns: 1fr;
  }

  .datetime-content {
    grid-template-columns: 1fr;
  }

  .year-links {
    gap: 0.3rem;
  }

  .year-link {
    padding: 0.4rem 0.8rem;
    font-size: 0.9rem;
  }
}