html, body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
  font-family: 'Noto Sans JP', 'Hiragino Kaku Gothic ProN', sans-serif;
  background: #fff;
  overflow: hidden;
}

body {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
}

.sp-frame {
  position: relative;
  width: 375px;
  height: 812px;
  background: #fff;
  overflow: hidden;
  border-radius: 16px;
  box-shadow: 0 2px 20px 0 rgba(50, 50, 80, 0.07);
  z-index: 1;
}

.bg-img {
  position: absolute;
  left: 0;
  top: 0;
  width: 375px;
  height: 812px;
  object-fit: cover;
  z-index: 0;
  pointer-events: none;
}

.head-title {
  position: absolute;
  left: 0;
  top: 24px;
  width: 100%;
  height: auto;
  max-width: 417px;
  z-index: 2;
  pointer-events: none;
  user-select: none;
  display: block;
}

.stone-area {
  position: absolute;
  top: 120px;
  left: 0;
  width: 100%;
  height: 560px;
  display: flex;
  flex-direction: column;
  align-items: center;
  z-index: 2;
  user-select: none;
}

.gage-area {
  position: absolute;
  left: 50%;
  top: 180px;
  transform: translateX(-50%);
  width: 226px;
  height: 50px;
  z-index: 3;
  display: flex;
  flex-direction: column;
  align-items: center;
  pointer-events: none;
}

.stone-gage-bar {
  width: 250px;
  height: 37px;
  background: #e0e0e0;
  border-radius: 2px;
  overflow: hidden;
  position: relative;
}

.gage-img {
  width: 250px;
  height: 37px;
  object-fit: cover;
  position: absolute;
  left: 0;
  top: 0;
  z-index: 2;
  pointer-events: none;
  clip-path: inset(0 100% 0 0);
}

.stone-img {
  margin-top: 110px;
  width: 340px;
  max-width: 90vw;
  z-index: 1;
  pointer-events: auto;
  user-select: none;
  display: block;
  touch-action: manipulation;
  position: relative;
}

.stone-btn-overlay {
  position: absolute;
  left: 50%;
  top: 220px;
  transform: translateX(-50%);
  width: 340px;
  height: 340px;
  z-index: 10;
  background: rgba(0, 0, 0, 0);
  cursor: pointer;
  border: none;
  outline: none;
  touch-action: manipulation;
}

.help-btn {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  bottom: 22px;
  background: none;
  border: none;
  padding: 0;
  z-index: 20;
  cursor: pointer;
  width: 118px;
  height: 46px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px rgba(80, 80, 80, 0.10);
  touch-action: manipulation;
}

.help-btn img {
  width: 100%;
  height: 100%;
  display: block;
}


/* ▼▼▼ 半透明の白い光が広がるエフェクト用のCSS ▼▼▼ */
#flash-overlay {
  visibility: hidden;
  pointer-events: none;
  position: fixed;
  top: 50%;
  left: 50%;
  width: 100vmax;
  height: 100vmax;
  z-index: 9999;

  background: radial-gradient(circle at center, 
    rgba(255, 255, 255, 0.9) 0%,
    rgba(255, 255, 255, 0) 70%
  );
  border-radius: 50%;
  
  transform: translate(-50%, -50%) scale(0);
}

#flash-overlay.active {
  visibility: visible;
  /* アニメーションを0.8秒に変更 */
  animation: fill-light 0.8s ease-out forwards;
}

@keyframes fill-light {
  from {
    transform: translate(-50%, -50%) scale(0);
    opacity: 1;
  }
  to {
    transform: translate(-50%, -50%) scale(2.5);
    opacity: 1;
  }
}