Is it good idea to create a game which includes 2d and 3d environment.
I mean that we have some times 2d environment, some times 3d environment. Environment changes based on mission.
A game I want to create includes a story as well as mission. 2d is good way to make amazing story. However, some mission requires 3d environment.
I have never seen a game including both 2d and 3d.
Is it a good idea?
Do you know any games based in this idea?
Sure. Go nuts 
Almost everyhting in Unity is 3D anyways so nothing stops you from setting a z-coordinate or rotating your 2D sprites.
I’m sure there are plenty of examples if you just know where to look.
One example is the demo project made by Unity back in the day when 2D was a new feature. At around 2 minutes 10 seconds
It’s an awesome idea and has been used a lot.
