I want to do something like a typing game. Would it be possible to create an Action where the user is represented a string. As soon as he presses this action a timer will start until he submits his own written string with another action which would stop the timer. Is this possible?
You can record starting and end time point by two independent transactions, but how will you check whether it's really typed by human instead of copy-and-paste? If you mean doing this by two actions in one transaction, time limit per each transaction is very short (a few milliseconds), because you should not possess blockchain network exclusively.