Love the look and feel to this! Cannon was fun to :). I really enjoyed playing this, and managed 9 out of the 10 souls :).
Feedback wise,.. suggest taking the camera a little further back, to have a bit more in the screen.
Need some info on the players health/lives. Some system of regaining health perhaps to, but somthing to let you know how close you are to err.. dying?,.. loosing :).
A Mini map, or some inidcation of where to go. You've gone for a search around style platformer set up, rather then a linear aproach. So hunting down one or two missing souls might get frustrating (saying that, I managed to find them all, just got taken out before the last one).
Great job, and really well done for this. As a fellow Solo Dev, I know how much work it can be doing this all yourself. Seems you made the art to! which is super impressive! Well done!