This week, I have been responsible for coming up with some ideas for enemies/map situations that can prove challenging to the player. No actual work can be done yet until some basic assets are completed. The enemy ideas I have so far are a basic small enemy that has to be dodged and a larger enemy that you have to roll to knock him down. Those could both be Mongolians of some form to be more bulky. Two flying enemies, one of which is something like a swarm of gnats that drains your score and another that is a delay then swoop attack. A ghostly enemy that can only attack you when your stealthed for a potential issue there. I would also like to try and find some way to work the Chinese Zodiac into the enemy pool but I can't think of a mechanic at this time that would make it quality.
As for game mechanics, a couple ideas are more traditional like having slick surfaces and other generic environmental items like falling rocks, crumbling ground, pits, etc. I also thought of making it so you can leap out of rolls so you can drop off an edge while rolling, get further distance then normal to get an item and then to leap out of it to get back to safety. Also, to have some areas that are stealth access only, like animals blocking a way when you come running through but when your stealthed, you can move into the area they were blocking. Also, the concept of bamboo branches or something that can sling you to higher areas and give you boosts. The only other big unique thing would be to implement a mechanic in a level that is light based, that otherwise limits visibility such as a lightning storm where you only see by lighting flash or torches near you that limits your visibility to half the normal amount.
As you can see, there are lots of ideas already there, more then enough to get through a first level. I am still working on coming up with other, new ideas and touching up some that were mentioned here. The main challenge has been coming up with unique ways for some of these ideas to work that doesn't make the game too difficult, replicate something too similar to existing ideas or over complicate the game with too many things to keep track of.