Flux is a fast, lightweight tweening library for lua.

Flux allows the user to easily interpolate a numerical value field of an object between its current value to a new value over a specified duration, using a specified easing type. If you want to do something like fade a sprite in or out, slide something onto the screen, gradually enlarge something or fade something from one color to another, Flux provides a means of doing this with a single function call.

-- Moves the ball object to the position 200, 300 over 4 seconds
flux.to(ball, 4, { x = 200, y = 300 })

Check out the README for instructions on setting up and using Flux in your projects. The github page for Flux is over here.