hows this? its very simple and u can only move left and right with the arrow keys. I think this is what ur askin for.
cls rgb (0,0,150)
get image 1,0,0,640,480
cls rgb (0,150,0)
get image 2,0,0,640,480
cls
ink rgb (150,0,0),0
x = 320
y = 240
image = 1
size = 5
do
paste image image, 0,0
circle x, y,size
if rightkey() = 1
x = x + 1
endif
if leftkey() = 1
x = x - 1
endif
if x > 640 - size
if image = 1
image = 2
else
image = 1
endif
x = 0 + 5
endif
if x < 0 + size
if image = 1
image = 2
else
image = 1
endif
x = 640 - 5
endif
loop
hope it helps