The concept is cool and the code is nice and compact. But that comes at a price. Your graphics could be greatly improved. I also think you could get away without the use of assembly by moving the snake itself up and down by changing the Y-Axis coordinates. You would have to use a variable to store the height, but it would greatly improve your graphics and increase speed a tiny bit.
live the life because the life is good —vivir la vida, porque la vida es buena
Vie la vie que la vie est bonne quod est bonum vitae in vita
lebe das Leben, weil das Leben ist gut —vivere la vita, perché la vita è buona