I am aware that this is not a research level mathematics question. Also, it would not have a single answer (if any) and yet, I hoping that it will be considered as a community wiki question worthy of MO attention.
About four months ago, I have created a website in honor of Maryam Mirzakhani. Timothy Gowers has kindly introduced it as follows.
[It is] a website in memory of Maryam Mirzahkani. I don’t mean that it is a memorial website: rather, it has taken an important aspect of her life — her interaction with other like-minded mathematicians at a young age — and aims to facilitate such interactions for others, by the setting up of maths4maryams groups.
It is just a start of an idea and with my nonexisting website making ability it is growing very slowly. I am hoping that the members of each group and the groups find their own way of mathematically interacting with each other without any intervention by the admins of the website (that is currently one!). However, I thought it would be nice if I could add one or two online interactive games on the main page of the website to break the ice.
Considering that the users of the website Mathematics 4 Maryams are mathematically inclined, I am wondering if there is any online interactive (mathematics) game you might want to suggest.