The world of 3D may seem a radical change from 2D, though it seems to be simply a case of an extra direction, the whole means of display and interaction totally changes in 3D. Our code needs to be able to handle that extra dimension and our graphics systems change considerably. BUT, the concepts of the games themselves don’t really change that much. You still have objects that you manipulate in normal code, you still have an environment to interact with, and you still have the basic game loops. 3D certainly adds a new direction, but, in general, the gameplay code isn’t going to change so much that you can’t adapt.