This is a really nice game! Its well-made.
The art style is great although certain lasers from certain enemies seem out of place...
From the files I see you did this with SDL!
How long did that take you!
Thanks, glad you liked it!
Yep, the gameplay code is C#, but the low-level code is C++ with SDL2 and a custom OpenGL renderer.
I did not really track development time, but I made The Lighkeeper on my spare time, and started around November of last year. Released it near the end of January. Then I updated it regularly ever since. So yeah, a few months of hard work. :)