I had too much physics in my life so my brain is screaming "Is energy and angular momentum conserved here???". I'm not sure if I'm a typical user :) What I dislike about influence areas is that sometimes small changes in the direction or speed makes big changes in the trajectory.

You may enjoy looking at another recent game "Hole Punch: Sling your spaceship around gravitational fields" https://notoriousbfg.com/hole-punch/ (HN discussion https://news.ycombinator.com/item?id=49946393 (364 points | 2 days ago | 90 comments))

About your game, three feature request:

* I'm not sure if it's a good idea to start the first game with so many weapons. I understand it's more fun, but not knowing what they do and the cost is confusing.

* In the weapon buying screen, it would be nice to have a visual representation of the explosion. (This looks like a very hard change. I'm not sure if you are going to add more features.)

* In the weapon buying screen, I prefer that the list is not cyclic, i.e. if I click down it stops when the list ends instead of cycling to the more expensive weapons again.