zscene: Easing actions

[ozkriff]

Something like http://www.cocos2d-x.org/wiki/Actions#Easing or Piston's https://github.com/PistonDevelopers/piston-examples/blob/master/src/sprite.rs .

Check https://docs.rs/easing and https://docs.rs/ezing

[ozkriff]

Also check https://github.com/wasm-network/tweek-rust