A lot of internal changes in this update, but also a couple of player-facing ones.
PC only (not smartphones): You might notice that the download size is significantly larger than normal. This is because starting with this version, all seasonal content (Christmas, Easter, Halloween, Thanksgiving) is bundled in. There is a button labelled “Seasonal Content” in the Options menu that will allow you to switch between seasonal editions on the fly. “Automatic” means that the game will use the current date to decide which seasonal edition to use (if any). Other buttons force a particular seasonal edition at all times. Note that, due to a technical restriction, this setting is reset every time the game is updated.
More details about this update can be found here: https://forum.chickeninvaders.com/t/ciu-version-137/29728