Thank you so much for asking! I used Clickteam Fusion 2.5 for this. Although, I wish I used Game Maker in the beginning considering my code in CF was a nightmare to read near the end. The development time on this took WAY too long. It should've only taken 1 month or even only about a couple of weeks to do.. but it went on embarrassingly for 5 months working on and off. Solely because of many mistakes I made throughout development. (I.e. Large sprites that are fully animated, planned out 50 levels, an overworld, multiple bosses, more enemies, ect.) I think if anything the actual gameplay with enemies took around a couple of weeks but it was the art that lengthened the development time because I was so invested in making it look pretty. (I should've focused on just finishing sooner with okay-looking art instead of what I made.) I totally don't regret it though as the knowledge I gained from it made me realize what I need to prioritize for my next game.