简单css动画 fadeIn fadeOut flash

@keyframes fadeIn{
    0%{
        opacity: 0;
        display: block;
    }
    100%{
        opacity: 1;
    }
}

@keyframes fadeOut{
    0%{
        opacity: 1;
    }
    100%{
        opacity: 0;
        display: none;
    }
}

@keyframes flash{
    0%{
        opacity: 1;
    }
    50%{
        opacity: 0;
    }
    100%{
        opacity: 1;
    }
}