CSS/矢印伸縮

#aDiv:hover #arrow{
    animation: stretch 0.6s linear infinite;
    -webkit-animation: stretch 0.6s linear infinite;
}
@keyframes stretch {
    40% { transform: translateY(0px) scale(0.8); }
    60% { transform: translateY(-10px) scale(1.1); }
    100% { transform: translateY(0px) scale(1.0); }
}