First official release of Red Falcon, a level editor for the US version of Contra on the NES…
This application lets you edit all 8 levels of the game. You can add sections to extend the length of the levels. You can add, remove and edit enemy types, position and properties. You can modify the color palettes for the background and the sprites, including the cycling colors. You can also change the Green Guys Generator sequences, found in Indoor levels. Several other visual options can assist the user in level design: grids, enemy indexes, enemy outlines, enemy search, player view, etc…
It is released under Mac OS X Mavericks (10.9), but it is backwards compatible down to Mac OS X Leopard (10.5), and should work on Mac OS X Yosemite (10.10). It can be run on 32 bits and 64 bits systems…

http://www.bwass.org/romhack/contra