Well I could replicate that example with an animation curve using only css: https://codepen.io/spartanatreyu/pen/YzbPjwg?editors=1100 https://codepen.io/sparta

Well I could replicate that example with an animation curve using only css: https://codepen.io/spartanatreyu/pen/YzbPjwg?editors=1100 https://codepen.io/spartanatreyu/pen/YzbPjwg?editors=1100 But if you want each step's duration to be parameterizable then you'll need to reach for js, I'd recommend the Animation API.