Great price but a there is a flaw

I am giving this 5 stars because compared to purchasing a ti-84 it is fantastic. A ti-84 is around $120 while this is only $6. We have ti-84s at our school and I prefer those because of the buttons being easier to use and press but they can do much about that because this is a touch screen phone. The one flaw I have found while using this is while zooming in closely to a line on the graph sometimes the line will move or extend a bit while I am zooming in then it will change positions when the zooming stops. I was graphing circles and just messing around with the app when I noticed this. I put y1=-sqrt(64-x^2) and y2=sqrt(64-x^2) and I noticed as I zoomed in to where they should presumably meet along the X axis they were messing up for me. Otherwise amazing app and I believe they actually have more features than a brand new ti-84.

KeithSmellBetter1491503 about GraphNCalc83, v1.5