That is a great question… I have some theories, but there is a lot going on… I can name a few… (Adding @Luxapodular )
[1] It is running in a web browser, but for some reason, if you play it directly in the Editor, the performance is a little bit better. I do have a good solid state Macbook Pro with a lot of processing power and RAM, so it is not my PC. I’m not sure how much memory my MAC assigns to one Chrome tab. That should be one of the problems.
[2] Everything was made using vector graphics. The benefit of the vector graphics is that no matter how much you scale them, you would see them crisp and nice. The downside is that it requires the computer processing/memory to do more math and process more things. I’m pretty sure that if I convert everything to PNGs, the game would perform at 30 FPS, which is the target FPS for this game demo.
[3] Cloning existing objects. In order for me to have more than one bullet, coin, block, enemy on the screen I had to create a main object (not at run time), then hide them in the black border, and then clone them for the game. Because of that, my game has several objects hide behind the scenes consuming small amounts of memory or processing. In Adobe Flash, I used to create a Clip, and then erase it from the scene, since Flash stored them into a library so then you could attach them at run time when needed. In this way I didn’t had to hide objects in the scene. This is something that the WickEditor developers should strongly consider to implement.