To make the "stock market" part more realistic, I would like it to be possible to make call and put options.
This would make it possible to speculate on companies without having to buy all the shares directly.
More information on these sites
https://en.wikipedia.org/wiki/Call_option
https://en.wikipedia.org/wiki/Put_option
https://fr.wikipedia.org/wiki/Call
https://fr.wikipedia.org/wiki/Put