For everyone asking for a save feature, there IS one. When starting the game, click "play game in HD". You will be sent to a website that lets you download the full game, play it in full screen, and save your progress for just $2. It's totally worth it. I hope he sells the submachine series in a bundle package.
Level 38 held me up the longest. I kept trying to multiply everything together, then I considered factorial, then I looked at the bird and figured it out. You should really use the bird for a solution to one or more of the levels.
This has the potential to be a full-scale game like plants vs zombies. Make the map chooseable and add about 10 more units to choose from, and maybe 10 more wand types. And probably 3 to 5 more world areas. So much potential here.
Good opportunity for our next game! Thanks for playing.