The current version includes 95% of all content. The remaining content (Vehicle No.8 and the final boss) is scheduled to be released in May or June.A bug exists with the "Black Hole Particle Cannon" in the current version, which will be fixed in a minor update within one to two days.
Source: Steam Community (opens in a new tab)
Build and release context
Recorded Steam release date:
Within one calendar day of this post (UTC). The listed date does not establish an exact launch time.