/* =========================================================================
   効果音（2026-09-26 採用）：ログインの案内と、音の ON/OFF
   ========================================================================= */
.startb { cursor: pointer; }
.startb__prompt {
  display: flex; align-items: center; justify-content: center; gap: 10px; margin: 18px 0 0;
  font-family: var(--f-en); font-weight: 700; font-size: 12px; letter-spacing: 0.3em; color: var(--paper);
  opacity: 0; transition: opacity 0.3s;
}
.startb__prompt::before { content: ''; width: 6px; height: 6px; border-radius: 50%; background: var(--lime); }
.startb__promptNote { display: block; margin-top: 6px; text-align: center; font-size: 10px; letter-spacing: 0.08em; color: var(--gray); opacity: 0; transition: opacity 0.3s; }
.startb.is-waiting .startb__prompt { opacity: 1; animation: sfxBlink 1.1s steps(2, end) infinite; }
.startb.is-waiting .startb__promptNote { opacity: 1; }
@keyframes sfxBlink { 50% { opacity: 0.35; } }

/* 音の ON/OFF（ナビの ENTRY の左） */
.sfx-toggle {
  display: inline-flex; align-items: center; gap: 8px; margin-left: auto; margin-right: 22px;
  font-family: var(--f-en); font-weight: 700; font-size: 11px; letter-spacing: 0.2em; color: inherit;
}
.nav .nav__entry { margin-left: 0; }
.sfx-toggle__icon { display: inline-flex; align-items: flex-end; gap: 2px; height: 12px; }
.sfx-toggle__icon i { display: block; width: 2px; height: 30%; background: currentColor; opacity: 0.6; }
.sfx-toggle.is-on .sfx-toggle__icon i { opacity: 1; animation: sfxBars 0.9s ease-in-out infinite alternate; }
.sfx-toggle.is-on .sfx-toggle__icon i:nth-child(2) { animation-delay: 0.2s; }
.sfx-toggle.is-on .sfx-toggle__icon i:nth-child(3) { animation-delay: 0.4s; }
@keyframes sfxBars { from { height: 25%; } to { height: 100%; } }
@media (max-width: 899px) {
  .sfx-toggle__label { display: none; }
  .sfx-toggle { margin-right: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  .startb.is-waiting .startb__prompt, .sfx-toggle.is-on .sfx-toggle__icon i { animation: none; }
}