Thanks for the great feedback - glad you enjoyed it.
If any complaint I was expecting to see, it would have been that it is too easy! During development I play tested an enormous amount and personally found it a bit too easy now, and can get to level 8/9 without much trouble. This is why I added the missile to the mothership just to make it a little more difficult. As a tip, when you get to the last invader, stand still and precision time aim rather than trying to chase and shoot. The speed is as per the arcade version and you will notice that the very last invader is subtly different in speed from left to right - this is by design as the same as the arcade. I always thought that was a hardware design issue in the old arcade hardware, but it turns out it was programmed that way.
Regarding CSpect emulation. I have tried to get it working under CSpect. Someone else commented that it didnt work under CSpect running NextOS which is why I compiled the BAT file variant for playing under CSpect. As to why it doesnt work directly under NextOS, thats a tricker question. I have spoken on the boriel/zxbasic forums about this, and so far, no diffinitive answer, but what is speculated by Mike (the cspect dev) is that there is no TBBLUE firmware, just the Nextos and emulator, so many system variables may not be as per real hardware on boot up. These can be set manually, if we know what they are, but that is the unknown at present. When ran from the batch file, the NextOS is not used - this is the difference - maybe that changes some vars. Yet, when ran from real hardware, it all works. All a big mystery at present. Compatability is better if you rename the file from SNX to SNA, and I have had success upto the point of the backdrop showing, but have got no further currently. My other next program, Funky Monkey Kid, does run under CSpect with NextOS as an SNA, which adds even more of a mystery for me. That game however uses very little next hardware - just the backdrop, real time clock, and save and load features. I speculate something to do with sprites or sound are the cause of the troubles in Spice Invaders on cspect/nextos as these are extra to whats in Funky Monkey Kid.
Rest assured, if we every find out the required settings, I will update and release.