Nice features, but very hard to use

This app has very good features, but I am giving it only two stars because its very hard to use. The function editor doesnt show you the current position where you edit, only if you start to use the selector tool... but then it is very hard to insert or remove something from the formula... you get frustrated and start from scratch, only to repeat all this again. For instance, you write sin, then 8, then pi, then x to make it sin(8*pi*x) but you get sin(8)*pi*x, you try to edit this by getting into the braces but may get sin(pi*x*8) and it refuses to draw this! Guys, please make it work like a normal text editor does, it is very hard to use this app.

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