Core workouts no legs

Hi I am just getting in to fitness and want to work on my core, I have a yoga mat but no other equipment. My main problem is that most core workouts I see involves using the legs. I am disabled and any use of my legs is very painful, even things like a plank position put too much pressure on my legs. I can still move them some but I would prefer minimal involvement, i can also get on and off the floor so they dont have to be seated exercises. Does anyone know where to look for this kind of workout? I have tried Google but its a bit overwhelming.