Thank you for taking the time to try the demo out, your feedback is invaluable to us! We will definitely think of adding more content to the demo. Regarding the fullscreen button for smaller devices, we will try to fix it ASAP as it was brought to our attention earlier as well. We apologize for the inconvenience!
Regarding the engine, we tried to make it seem more polished compared to several peers using this engine. However, we've come to accept its limitations. so for the final product we will definitely, definitely be porting it to Ren'Py. For demos we may still use Tyrano, but you can be assured that we will bring the best user interface possible to the end product.
We will keep updating the demo, and we really value feedback like yours! Thank you for following us! :)