Trove Tweens is a toolkit for tweening in ECS. Tweens are simple procedural value animations that are handled entirely through code rather than being pre-baked into animation clips.
We call this a tweening "toolkit" rather than a tweening "system", because it requires more manual work and decisions to be made by the user compared to the usual popular tweening solutions of classic OOP Unity, where you can simply tween anything from anywhere in any way. The upside, however, is that the tweens created with this toolkit can be highly efficient and used at a large scale. If you need thousands units in your game that get a color flash and shake when receiving damage (or you have less units but don't want this visual feedback code to take a significant portion of your frame budget), this is the solution for you!