Text selection is broken – Calca Review

I love the desktop version but on the iPhone this is unusable. It's impossible to edit the text. Enter an expression like 9*8+12*8 then try and change the plus to a minus. It keeps selecting ranges over the numbers instead of letting you position the cursor. I guess the answer is to just insert a lot of spaces to work around the "cleverness" of the app. Update: the spaces don't work because it helpfully ignores them and goes into select mode.
Review by graveltech on Calca.