ネオン風ボタン（暗色背景サイト向けにも）

<div class="push-button_box">
  <a href="#" class="push-button neon-style">参加する</a>
</div>

.push-button_box{
  width:30%;
  margin:50px auto;
}

.push-button.neon-style {
  display: inline-block;
  width: 100%;
  padding: 14px 0;
  background: #111827;
  color: #0ff;
  font-size: 16px;
  font-weight: bold;
  text-align: center;
  text-decoration: none;
  border-radius: 8px;
  box-shadow:
    0 0 5px #0ff,
    0 0 10px #0ff,
    0 0 20px #0ff;
  transition: 0.2s ease;
}

.push-button.neon-style:hover {
  background: #0f172a;
  box-shadow:
    0 0 10px #0ff,
    0 0 20px #0ff,
    0 0 30px #0ff;
}