I think the word is "remainder". I must say I'm totally impressed by the whole thing. Just like the orriginal but in my favoured medium. I would think that your system of 320 2px animated mc's would have taken you ages! Did you perhaps consider just using 4px square mcs and duplicating them?
Are you going to allow for caverns? Remmeber the original had cavern maps with a ceiling as well as a floor... how about rollers? (My personal favourite weapon).