I always thought that planning is important for a game. But i don't know at which point. Some are telling me to code instead of planning but i feel like its still important because when you will be in the code you will know what to do next more easily. I am currently working on a game that will have lots of content so i decided to start a design document introducing thoses content and at a side-level i am doing proofs of concept to check if it can be done. Parts of each proofs of concept then could be used later in the real game.

EDIT: I am working alone on this project.

So my question is : It is worth planning before jumping in the code ? Im still interested to know what others have to say about this. Cause i still get some poeple saying i should code instead of thinking.. so what your opinion on this ?