@LGB: Sorry, I was not reflecting on the emulators, just my general thoughts about the "C65 Software Development" theme here. Mentioning the "mono check" was an abstract parallel for relation between the C65 and the MEGA65 - like a sound engineer when making a stereo mix, he always needs checking the mono compatibility of that (for radios and other sound systems). Similarly, when developing for the MEGA65, it might be useful to be able to be comfortably checking backward compatibility with all possible other implementations of the C65 environment(s), for the safety (or vice versa, when developing for the C65, checking if it also runs on MEGA65). Sorry for the misleading. :) I didn't know what the intention of mentioning these two things together was here; only saw this topic coming up and threw my personal point of view on top of that.