Marvellous Inc. is an open source programming game. It can be found on Steam. Source code is available. It is written for Love 0.10.2. It does not work on Love 11.2. I've made some quick changes to get it running. It probably still has bugs.
I'm able to enter the o character without a problem. You're using my fork with love 11.2? It seems to register a key on your screenshot. Does it have the o but just not display it?