body {
  margin: 0;
  padding: 0;
  font-family: 'Helvetica Neue', sans-serif;
  background: url('assets/website_background.png') no-repeat center center fixed;
  background-size: cover;
  color: #333;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  min-height: 100vh;
  backdrop-filter: brightness(0.9);
}

.container {
  margin-top: 50px;
  background: rgba(255, 255, 255, 0.85);
  padding: 2rem;
  border-radius: 16px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
  max-width: 600px;
  width: 90%;
}

h1 {
  text-align: center;
  color: #444;
  font-size: 2em;
  margin-bottom: 1rem;
}

h2 {
  margin-top: 2rem;
  color: #555;
}

a {
  color: #1e90ff;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.social-icons {
  display: flex;
  gap: 20px;
  margin-top: 1rem;
}

.social-icons a {
  font-size: 1.5rem;
  color: #555;
  transition: color 0.3s;
  position: relative;
}

.social-icons a:hover::after {
  content: attr(title); /* title属性の内容を表示 */
  position: absolute;
  bottom: -30px;
  left: 50%;
  transform: translateX(-50%);
  background: #333;
  color: #fff;
  padding: 5px 10px;
  border-radius: 5px;
  font-size: 0.8rem;
  white-space: nowrap;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
  z-index: 10;
  opacity: 1;
  transition: opacity 0.3s;
}

.social-icons a:hover::before {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  border-width: 5px;
  border-style: solid;
  border-color: #333 transparent transparent transparent;
  z-index: 10;
}

.social-icons a::after {
  opacity: 0;
  pointer-events: none;
}

/* ローディングアニメーション */
#loading {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(255, 255, 255, 0.9);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
}

.spinner {
  border: 4px solid rgba(0, 0, 0, 0.1);
  border-top: 4px solid #333;
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}