.hi-background {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: -1;
  pointer-events: none;
  overflow: hidden;
  
  /* Hikari theme (light) */
  &[data-theme="hikari"] &__gradient {
    background: radial-gradient(
      circle at center,
      rgba(245, 245, 245, 0.9) 0%,
      rgba(255, 182, 193, 0.8) 30%,
      rgba(255, 105, 180, 0.7) 60%,
      rgba(219, 112, 147, 0.6) 100%
    );
  }
  
  /* Tairitsu theme (dark) */
  &[data-theme="tairitsu"] &__gradient {
    background: radial-gradient(
      circle at center,
      rgba(25, 35, 55, 0.95) 0%,
      rgba(45, 55, 85, 0.9) 30%,
      rgba(65, 75, 105, 0.85) 60%,
      rgba(25, 35, 55, 0.8) 100%
    );
  }
}

.hi-background__gradient {
  position: absolute;
  width: 150vw;
  height: 150vh;
  top: -25vh;
  left: -25vw;
  will-change: transform;
  
  /* Hikari theme (light) */
  .hi-background[data-theme="hikari"] & {
    background: radial-gradient(
      circle at center,
      rgba(245, 245, 245, 0.9) 0%,
      rgba(255, 182, 193, 0.8) 30%,
      rgba(255, 105, 180, 0.7) 60%,
      rgba(219, 112, 147, 0.6) 100%
    );
    animation: gradient-move-hikari 60s linear infinite;
  }
  
  /* Tairitsu theme (dark) */
  .hi-background[data-theme="tairitsu"] & {
    background: radial-gradient(
      circle at center,
      rgba(25, 35, 55, 0.95) 0%,
      rgba(45, 55, 85, 0.9) 30%,
      rgba(65, 75, 105, 0.85) 60%,
      rgba(25, 35, 55, 0.8) 100%
    );
    animation: gradient-move-tairitsu 60s linear infinite;
  }
}

/* Hardware-accelerated animations using transform */
@keyframes gradient-move-hikari {
  0% {
    transform: translate(0, 0) rotate(0deg);
  }
  25% {
    transform: translate(10vw, 0) rotate(90deg);
  }
  50% {
    transform: translate(10vw, 10vh) rotate(180deg);
  }
  75% {
    transform: translate(0, 10vh) rotate(270deg);
  }
  100% {
    transform: translate(0, 0) rotate(360deg);
  }
}

@keyframes gradient-move-tairitsu {
  0% {
    transform: translate(-5vw, -5vh) rotate(0deg);
  }
  25% {
    transform: translate(15vw, -5vh) rotate(90deg);
  }
  50% {
    transform: translate(15vw, 15vh) rotate(180deg);
  }
  75% {
    transform: translate(-5vw, 15vh) rotate(270deg);
  }
  100% {
    transform: translate(-5vw, -5vh) rotate(360deg);
  }
}