Maybe if you didn't use any of the fanciness... XRoar's become a lot more resource-hungry over the years, as reasonable assumptions of available desktop power climb. It might mean reverting some of the stuff that happens cycle-by-cycle now but used to be bunched up inaccurately for speed. And the video code often needs rethinking to fit the target device.
But portable Dragon is how it started! GPRoar as it was then for the GP32 worked pretty well, considering. And later on the Nintendo DS port was good fun - playing Buzzard Bait on the train into work
Both of those needed some fun thinking though - the GP32's screen is kinda rotated 90° in memory and I think I had it drawing four scanlines at a time for speed (4 * 8-bit values leading to 32-bit-at-a-time writes, which was important to reduce memory bandwith use and not interfere with audio), and I think the fastest way to do video on the NDS was to break the screen up into huge low-bit-per-pixel sprites
