・Lasers at LV. 4 and LV. 11 now penetrate walls.
・Background music has been added. You can turn the background music and sound effects on or off from the title screen.
・Enemy colors are now determined by HP rather than by wave.
HP 3 or less: White
HP 4–5: Light blue
HP 6–7: Yellow
HP 8–9: Orange
HP 10 or more: Red