What do you think about trading simulators? I am making research on stock simulators – your opinion matters

Hi community!

I'm currently doing research on trading simulators, and I would love your opinion on what things should be in the good trading simulator/trading course.

I would also love your opinions on what are the top things you are looking for when choosing a trading simulator. For example, what is more important to you – design or functionality, etc.?

Maybe you even can share your most loved stock trading simulator or maybe the one which you think is the worst and why?

Your opinions will really help me in my research!