* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: Arial, sans-serif;
}

body {
  font-family: Arial, sans-serif;
  line-height: 1.6;
  color: #333;
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
  background-color: #f5f5f5;
}

header {
  text-align: center;
  padding: 20px 0;
  margin-bottom: 30px;
  background-color: #1a237e;
  color: white;
  border-radius: 5px;
}

header h1 {
  margin-bottom: 10px;
}

main {
  display: flex;
  flex-wrap: wrap;
  gap: 30px;
  justify-content: center;
}

@media (min-width: 768px) {
  main {
    grid-template-columns: 2fr 1fr;
  }
}

section {
  background-color: white;
  padding: 20px;
  border-radius: 5px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
  width: 100%;
  max-width: 500px;
}

section h3 {
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 1px solid #ddd;
  color: #1a237e;
}

.activity-card {
  margin-bottom: 15px;
  padding: 15px;
  border: 1px solid #ddd;
  border-radius: 5px;
  background-color: #f9f9f9;
}

.activity-card h4 {
  margin-bottom: 10px;
  color: #0066cc;
}

.activity-card p {
  margin-bottom: 8px;
}

.form-group {
  margin-bottom: 15px;
}

.form-group label {
  display: block;
  margin-bottom: 5px;
  font-weight: bold;
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 4px;
  font-size: 16px;
}

button {
  background-color: #1a237e;
  color: white;
  border: none;
  padding: 10px 15px;
  font-size: 16px;
  border-radius: 5px;
  cursor: pointer;
  transition: background-color 0.2s;
}

button:hover {
  background-color: #3949ab;
}

.message {
  margin-top: 20px;
  padding: 10px;
  border-radius: 4px;
}

.success {
  background-color: #e8f5e9;
  color: #2e7d32;
  border: 1px solid #a5d6a7;
}

.error {
  background-color: #ffebee;
  color: #c62828;
  border: 1px solid #ef9a9a;
}

.info {
  background-color: #d1ecf1;
  color: #0c5460;
  border: 1px solid #bee5eb;
}

.hidden {
  display: none;
}

footer {
  text-align: center;
  margin-top: 30px;
  padding: 20px;
  color: #666;
}

.participants-section {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px dashed #eee;
}

.participants-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.participants-toggle {
  background: transparent;
  border: none;
  color: #1a237e;
  cursor: pointer;
  font-weight: 600;
  padding: 4px 8px;
  border-radius: 4px;
}
.participants-toggle:hover {
  background-color: rgba(26,35,126,0.08);
}

.participants-list {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  list-style: none;
  padding: 0;
  margin: 0;
}

.participant {
  display: flex;
  align-items: center;
  gap: 8px;
  background: linear-gradient(180deg, #ffffff, #f7f9ff);
  border: 1px solid #e6e9ff;
  padding: 6px 10px;
  border-radius: 20px;
  font-size: 13px;
  color: #333;
  box-shadow: 0 1px 2px rgba(13, 17, 43, 0.04);
}

.avatar {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background-color: #1a237e;
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 12px;
}

.participant-email {
  max-width: 160px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.remove-btn {
  background: transparent;
  border: none;
  color: #c62828;
  font-weight: 700;
  margin-left: 6px;
  cursor: pointer;
  padding: 0 6px;
  border-radius: 50%;
}

.remove-btn:hover {
  background: rgba(198, 40, 40, 0.08);
}

/* small helper */
.participants-empty {
  color: #666;
  font-size: 13px;
}