Can you share any more details about the Pong port? I have been collecting various bits of information about u'nSP processors, particularly the SPG2xx series used in mid 2000s plug-and-play games, but so far I have never seen an actual homebrew game for any of these chips (with the exception of the Mattel Hyperscan's SPG293, which however uses a different architecture).

I have also been looking into the newer GeneralPlus GPM4x30 SoCs used by some modern Chinese plug-and-plays with HDMI output, at least by the ones that aren't straight up Famiclones hardwired to a composite to HDMI upscaler. Those are ARM based so much less of a pain to reverse engineer but also much less fun...