Hello again. I am trying to make a PONG clone using SB4. I tried using GBOX/GFILL to make a box as the paddle. The problem is that the box is like flickering. Did I do something wrong with me code? 
[SB4] GFILL and ACLS
ACLS is slow. It's only meant for complete resets of the display. To erase only the graphic page, use GCLS. Also, using LOOP ENDLOOP is preferable to using a GOTO label loop.
'acls at the beginning to reset the display ACLS LOOP 'gcls in the loop to erase the graphics. GCLS GBOX 100,100,200,200 VSYNC ENDLOOP