Another way is to set the backdrop on, which is a good point to understand.
The default is
BACKDROP OFF. This means it's up to you to clear up the background in between SYNCs. Run the following 2 snippets, and you'll soon understand what setting the background on does for you...
Backdrop Off
sync on: sync rate 30
backdrop off
make object cube 1, 20
do
rotate object 1, object angle x(1) + 1,object angle y(1) + 1,object angle z(1) + 1
color object 1, rgb(127 + rnd(128),127 + rnd(128),127 + rnd(128))
sync
loop
end
Backdrop On:
sync on: sync rate 30
backdrop off
make object cube 1, 20
do
rotate object 1, object angle x(1) + 1,object angle y(1) + 1,object angle z(1) + 1
color object 1, rgb(127 + rnd(128),127 + rnd(128),127 + rnd(128))
sync
loop
end
Text without smudge:
sync on: sync rate 0
backdrop on
for n = 1 to 20
time = timer()
while timer() < time + 500
text 100,100, str$(n)
sync
endwhile
next n
BACKGROUND ON has overheads, and will slow your game down. But until you get to a stage where the screen is completely filled with 3D objects (such as a Skybox for a background), it's essential.