Like many, I dont care much about visuals or music. A old school slot with great mechanics beats any new super nice graphic slot if the slot mechanics are poor.
I believe you can do that on Mancala and Voltent (wazdan).
Playngo slots would heat the back of your phone back in the day. When moon princess trinity came out my phone would freeze as you can have so many connections in one spin. Thank god they fixed it.
No interest in super fancy graphics as I mostly play on laptop with integrated gpu etc so it makes my system fan spin etc. Allowing players to toggle quality settings etc would be good.