I have an alternate branch available in Steam, where I sometimes publish experimental features or possible game play changes before being incorporated into the main/default branch. It is called 'beta' and can be accessed from the BETA tab in the Steam game properties window. Currently this branch is hosting several game play tweaks that I think may help address some "slow burn" issues in the first several levels, as well as fine tune some of the boss fights. If you are up for it, feel free to try it out and let me know what you think about the proposed changes good or bad.

Gameplay changes

• Added some mini bosses/enemies to the end of the first level. Previously there were no bosses, as level 1 was designed around taking time to move about and practice hunting asteroids, picking up power-ups/tokens. However, several comments have indicated that the game starts of slow, so hopefully this helps to balance this. The design of these ships may change as I'm reusing assets from the first boss (Terminator) right now.
• Instead of the shield power-up being the first power-up that you can pick up I have moved it later in the game (sorry), and instead introduced the rapid fire power-up at level 1.
• Level 2 now unlocks the "nuke" power-up given the player one of the Defensive power-ups much earlier.
• Bosses are a little tougher from a damage point of view.
• When new bosses are encountered, they are now usually accompanied by one (or more) previous bosses to keep things a little more difficult. No more do you get to fight one "serpent/worm" in isolation where they are the weakest. I still have some things planned later for the serpent ship that should help as well.
• The "shotgun" burst power-up has been weakened slightly.
• Bosses used to spawn at the edges of the arena, like asteroids do. This has been changed to spawn at other non-visible locations on the map more centrally (warping in or something). This avoids more boss fights at the edge of the screen which didn't work as well with the wrapping nature of the arena.