I'm terribly sorry to report some issues with the game First, inability to change controls is a deadly sin here, my el cheapo keyboard gets specific keys locked with certain diagonal + fire keypresses combinations. Secondly, two or three times final boss refused to appear. It was always when I had near-perfect runs, getting hit only on the last stage. At the near-end of the last stage, I've been seeing green fighter flashing blazing fast thru the entire screen for a few frames. Then, warning message simply didn't appear, aand I could notfinish the game, just fly infinitely. Obviously, bug got itself fixed when I tried to record it with OBS :/ Third issue... or is it an issue, or design? Plasma gun is the most powerful weapon, being able to sent upward and downward shots as quickly as I can rapid-shmash back and front fire one after another. And, finally, a question. any extra levels, hidden features if I 1CC the game or beat with all pick-ups collected? and, finally, firstname.lastname@example.org does not work. Of course I had to check that out first.
Sorry to hear about bugs. It seems regardless of how much you test things yourself there will always be bugs.
I think I've triggered the boss bug when I made an engine update and have a fix for it. However, as I need to re-test everything it's unlikely I will release an updated version anytime soon.
Regarding control remapping, you are absolutely right, it should have been there. My engine has currently no support for it, but it's definitely something I should look into.
Finally I'm sorry to inform you that there are no extra levels or hidden features. The only thing that exists is unfinished levels or level concepts at my machine at home.
The game was actually made as a proof of concept for my game engine and after 4 levels I felt quite done with the game. There never was much thought put into the design, so the plasma gun is probably very OP. Foolishly I decided to make a shmup as I thought it would be easy. Boy was I wrong! A shmup requires constant action and variation.
As some time have passed since I finished Death Strike I must confess I have been toying with the idea of a sequel, Super Death Strike. Who knows, maybe it will be a spring project?