1. Initial Planning
This is where you plan the concept of your games. There are no creations yet, just plans and discussion about what game to create. The ideas are limitless. It would be best to do rough drafts first. Solidify it by discussing the pros and cons of every idea and researching various stuff. Take references from other games or the real world itself.
Optimal time range: 3 days to 1 month
Case study reference: Our Obby Game in Roblox was planned within 3 days.