Border Down is a horizontally scrolling
shoot 'em up video game developed and published by
G.rev.
The story takes place in the future where humans are defending their
Mars
colony from an invading alien attack.
The game employs a "border
system" where each stage has three variations of different difficulty.
The player starts on the easiest variation, and is lowered to a more
difficult variation with each subsequent loss of a
life.