1) Choose a type of game 2) Don't reinvent the wheel I would suggest to take advantage of the library of open source games with source code available to explo

1) Choose a type of game 2) Don't reinvent the wheel I would suggest to take advantage of the library of open source games with source code available to explore. Maybe you could improve an open source game instead to create a new one If is an adventure game, you could just design a new campaign for Wesnoth. My advice would be to make a role game. With cool design and some bits of still 3D here and there. It can use a mix of techniques, so you can take advantage of it to teach your child lots of new concepts. Is easy. Much less frustrating than trying to recreate Saint Andreas type games. You don't need to mess with physics or how to make your characters walk an jump without glitches. Can be finished in a weekend. Just a good history, several pictures of locations and some cards of characters to interact around. You can start with really simple rules and a few characters and call it a day. Mission accomplished. Can be expanded. Add it more and more rich and interesting later, so your child will be entertained for much more time. Is creative. Ask your son to design characters and monsters first and then draw the cards yourself. You could use an image manipulation program or use Stable diffusion to give life to your child ideas in realistic characters and cards, and your son will absolutely love it. 3) Don't use copyrighted material to create your game. Is teaching the wrong lazy lesson to your child. If you need a location background just use your own photos. Remember Flappy bird and use the game as an opportunity to educate your child in good practices. 4) If you feel brave, use blender for creating a small 3D scenery, or mm3d/freecad etc to draw detailed maps of buildings and areas.