The colors are heavily based on the HP Prime version of this game and to my surprised, xLIBC colors had a very good range that made it possible to mimic the HP game as much as possible. The only difference was the fonts and lack of real-time score update.
Speed-wise, the main issue right now is that xLIBC splits the display in two buffers, but those buffers cannot be shifted around. If we could do that then we could simply redraw every sprite at the exact same location each frame and shift the screen (and buffers) around. Another idea would be to allow drawing sprites/shapes outside the 160 pixels range that the buffer offers, if the user specifies an extra optional argument called OFFScreenDrawEnable (set to 0 or nothing if disabled and 1 if enabled). I'm unsure how hard this would be to implement, though.
That said, it depends if you still plan to update xLIBC and if the 84+CE/83PCE allows hardware scrolling and half-res mode.