A thinking aloud post. Aside from the key limitation imposed by Apple guidelines of no external program loading, it was obvious that long term appeal for the app was going to be marred by the virtual keyboard for gamers. The keys are too crowded and/or small depending on the iOS device.
Hence, development focus recently has been a virtual gamepad mode. This consists of an area to simulate a directional joy pad control and up to four large game keys. On selecting the software the gamepad is pre-configured to map to the default keys with an option to redefine. See the screen shots of the work in progress.

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The directional joystick control is based on a threshold distance from its centre. When a tracked touch exceeds the threshold the mapped direction key state is on. When released the touch joystick gracefully returns to the neutral centre no key press state. Diagonal movements map to the up/down and left/right keys pairs being simultaneously on.
The results weren't quite what was hoped. Particularly true for games that didn't allow two simultaneous key presses to be processed, which lead to a few ideas:
i) A user setting to alternate between the joystick control or the four discrete directional keys in a diamond layout.
ii) A user setting to prioritise allowing one key press to be registered at a given time. Starting in order of preference the non direction keys and then the furthest pressed directional key.
iii) The other possibility was to have a burst mode where directional movement registers a series of key presses as opposed to a single long key press.
Has anyone else had any experience mapping ZX80/81 emulated keys to a virtual gamepad control? Thoughts?
On a brighter note I find it a lot easier to progress on the Mojon Twins' titles using the new controls.
I'll also make time to add ZXpand joystick support for supporting titles. The above needs some polish so it's a couple of weeks away before I have time to refine and submit to Apple.
Kevin