3D Rad is a free game creation software. To build a game of relatively complex complexity, the program is very simple indeed. There are many examples that come with 3D Rad.
As well as light and sounds you can apply particle and texture effects to game architecture, and make animations from them. An opacity layer can be applied to create textures in 3D. Artificial intelligence is present (in the project database there are examples of AI).
It could rain or snow during the daytime, for example. An effect must be applied to this. Besides the weather conditions, you can decorate your gameplay with spots, blur, glare, water, er with weather conditions, you can decorate your game with light spots, blurring, glare, water, etc. Objects such as fog, fire, mirror, etc.