.welcome-letter-overlay {
  position: fixed;
  inset: 0;
  z-index: 5000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 24px;
  background: rgba(0, 0, 0, 0);
  opacity: 0;
  transition: background 350ms ease, opacity 350ms ease;
}

.welcome-letter-overlay.is-visible {
  display: flex;
}

.welcome-letter-overlay.is-active {
  background: rgba(0, 0, 0, .55);
  opacity: 1;
}

.welcome-letter-stage {
  width: min(900px, 90vw);
  max-height: 94vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 18px;
  opacity: 0;
  transform: scale(.95);
  transition: opacity 350ms ease, transform 350ms ease;
}

.welcome-letter-overlay.is-active .welcome-letter-stage {
  opacity: 1;
  transform: scale(1);
}

.welcome-letter-scroll {
  width: 100%;
  max-height: calc(90vh - 70px);
  overflow: auto;
  overscroll-behavior: contain;
  border-radius: 0;
  scrollbar-width: thin;
}

.welcome-letter-image {
  display: block;
  width: 100%;
  height: auto;
  margin: 0 auto;
  user-select: none;
  -webkit-user-drag: none;
}

.welcome-letter-start {
  flex: 0 0 auto;
  width: 220px;
  height: 52px;
  border: 0;
  border-radius: 12px;
  background: #2563EB;
  color: #FFFFFF;
  font-size: 16px;
  font-weight: 900;
  cursor: pointer;
  transition: background 180ms ease;
}

.welcome-letter-start:hover {
  background: #1D4ED8;
}

body.welcome-letter-locked {
  overflow: hidden;
}

@media (max-width: 768px) {
  .welcome-letter-overlay {
    padding: 24px 0;
  }

  .welcome-letter-stage {
    width: 90vw;
    max-height: calc(100vh - 48px);
    gap: 14px;
  }

  .welcome-letter-scroll {
    max-height: calc(90vh - 66px);
  }

  .welcome-letter-start {
    width: min(220px, 78vw);
  }
}