Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics
SalesBundles
Jobs
Tags

Disclaimer: I am not a lawyer, so this is not legal advice and its mostly based on my common sense and stuff ive read/learned over the years. 

I think you are allowed to copy game mechanics and game feel. Where i think you start running into issues is when you make something that is way too similar. 

For example: i make a game called "creature catcher" where you go around catching monsters training them by battling other monsters in order to defeat stronger adversaries(Pokemon clone). This would be ok as along as it was not too similar to the actual pokemon franchise. If for some reason i used a logo named "ninlendo" and my game was called "PocketMons" with similar font and color as pokemon logo then i would run into some trouble. 

Some companies are more aggressive about protecting their brand/trademark so be aware of that as well. 

In the end if i was you, i would just avoid making anything that too closely resembles something else to avoid any legal issues. If you do decide to continue on this route i would recommend you get some real legal advice from someone who is qualified. 

Thanks! I had thought that we had some artistic freedom, but I will take your advice and revise my graphics accordingly.