Thank you for trying out the game. Yes, the events are completely random and non-repeatable; each of them can only occur once (except for the 'period of calm' events, of which there are 5). Currently, there are 31 events in total, and a maximum of 25 can occur. For the future update, I plan to expand the events to 50 and distribute them on a scale from easy, to medium (mid-game), to difficult (end-game). Thanks again for your feedback :)