html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background-color: #ffffff;
  color: #000000;
  font-family: sans-serif;
}

#app {
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center; /* タイマー + ボタンを中央に寄せる */
  align-items: center;
}
.timer {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 20vw;
  font-family: monospace;
  transition: opacity 0.25s ease;
  text-align: center;
  margin-bottom: 0;
}

.flash {
  opacity: 0;
  animation: blink 0.5s ease-in-out;
}

@keyframes blink {
  0%   { opacity: 1; }
  25%  { opacity: 0; }
  50%  { opacity: 1; }
  75%  { opacity: 0; }
  100% { opacity: 1; }
}

.controls {
  display: flex;
  gap: 30px; /* ボタン間のスペース */
  justify-content: center; /* タイマー + ボタンを中央に寄せる */
}

button {
  font-size: 1.5rem;
  padding: 10px 30px;
  border: none;
  border-radius: 8px;
  background-color: #007bff;
  color: white;
  cursor: pointer;
  transition: background-color 0.2s;
}

button:disabled {
  background-color: #555;
  cursor: not-allowed;
}

button:hover:enabled {
  background-color: #0056b3;
}

.footer {
  text-align: center;
  position: fixed;
  bottom: 0;
  width: 100%;
  background-color: #ffffff;
  padding: 10px 0;
}

.footer-logo {
  width: 50%;
  max-width: 100px;  /* 最大サイズ */
  height: auto;
  display: block;
  margin: 1rem auto 0; /* 上に余白、中央寄せ */
}