It's very simple method. I stacked a lot of sprites along Z axis. This method gets a heavy load on SmileBASIC and reduces CPU process speed. I don't know the reason why exactly. In my opinion, if I shrink sprite size, SmileBASIC will drive faster.
Biography on my profile?
I've written just introduction to keys of SmileBASIC programs I've made as follows.
RAPAE8D: it includes various kinds of programs
CACQ33L4: aircraft landing simulator
JEE3V3NE: samurai sword action
L4DXQ384: like "simon says" but it depends on Japanese
Y33NQ54S: wandering around the maze
VKAKV3ZP: car racing
DSEEX3QJ: supersonic kite racing
DEEE33Q4: golf