.btn{
  display: inline-block;
  padding: var(--sp-2) var(--sp-4);
  border-radius: var(--radius);
  border: 1px solid var(--c-border);
  background: #fff; text-decoration: none;
  transition: transform .08s ease, background .2s ease;
}
.btn:hover{ background: var(--c-surface); }
.btn:active{ transform: translateY(1px); }
.btn--primary{ background: var(--c-primary); color: #fff; border-color: transparent; }
.btn--ghost{ background: transparent; color: var(--c-primary); border-color: var(--c-primary); }

.card{
  background: #fff; border: 1px solid var(--c-border); border-radius: var(--radius);
  padding: var(--sp-5); box-shadow: var(--shadow);
}
.card__title{ margin-top: 0; }
.card__body{ color: var(--c-muted); }

/* トップへ戻るボタン */
.scroll-to-top {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: 2.75rem;
  height: 2.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255, 255, 255, 0.15);
  backdrop-filter: blur(10px);
  color: rgba(255, 255, 255, 0.9);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 50%;
  text-decoration: none;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease, background 0.3s ease, border-color 0.3s ease;
  z-index: 100;
  font-size: 0.9rem;
}

.scroll-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.scroll-to-top:hover {
  background: rgba(255, 255, 255, 0.25);
  border-color: rgba(255, 255, 255, 0.3);
  color: #fff;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.scroll-to-top:active {
  transform: translateY(0);
}

@media (max-width: 767px) {
  .scroll-to-top {
    width: 2.5rem;
    height: 2.5rem;
    bottom: 1.25rem;
    right: 1.25rem;
    font-size: 0.8rem;
  }
}