The player objects consist of a 16 color sprite (which is done by combining two sprites). This is combined with two 4 color sprites which make up the shields on either side of the player.
The shots are normal 4 color sprites. Since sprites are only limited in width (to 16 pixels) the shots can grow extremely high which can be seen on the far right with the pink bullets.
The bonus pickups are normal BOBs (Blitter OBjects). They are drawn traditionally to the screen.