/* DTD MOD - auto shake buttons (every 3s) */
@keyframes dtd-wiggle-3s {
  0%   { transform: translate3d(0,0,0) rotate(0deg) scale(1); }
  2%   { transform: translate3d(-2px,0,0) rotate(-1.6deg) scale(1.01); }
  4%   { transform: translate3d( 2px,0,0) rotate( 1.6deg) scale(1.01); }
  6%   { transform: translate3d(-2px,0,0) rotate(-1.2deg) scale(1.01); }
  8%   { transform: translate3d( 2px,0,0) rotate( 1.2deg) scale(1.01); }
  10%  { transform: translate3d(-1px,0,0) rotate(-0.8deg) scale(1.005); }
  12%  { transform: translate3d( 1px,0,0) rotate( 0.8deg) scale(1.005); }
  14%  { transform: translate3d(0,0,0) rotate(0deg) scale(1); }
  100% { transform: translate3d(0,0,0) rotate(0deg) scale(1); }
}

/* Áp dụng cho nút tải (btn) */
a.btn{
  will-change: transform;
  transform: translateZ(0);
  animation: dtd-wiggle-3s 3s ease-in-out infinite;
}

/* Để không “lắc đồng loạt” nhìn chán: lệch nhịp theo vị trí */
.stack a.btn:nth-child(3n+1){ animation-delay: 0s; }
.stack a.btn:nth-child(3n+2){ animation-delay: 0.35s; }
.stack a.btn:nth-child(3n){   animation-delay: 0.7s; }

/* Tôn trọng người dùng bật Reduce Motion */
@media (prefers-reduced-motion: reduce){
  a.btn{ animation: none !important; }
}