ok i will say one thing really fast. for a metal slug style game you will want some kind of scripting. calc or not it is doable. and if done properly will make the whole project insanely easier to manage in group format. how you ask simple
by scripting it you can have each person work on different aspects of the script system. one person works on the drawing commands one works on the players attacks ect
by using a good interupt scheme you can work threw the whole mess while keeping up on collision detections and achieve good quality graphics.
also if you hard code it it will be to large to fit a decent amount of levels/content. with scripting and compression it will take a lot less space i belive
also from experiance i say use 3 level greyscale if at all possible will allow you to have a background for detail/professional look but still keep everything easy to see.
(keep in mind tho im asm which is a bit more optimized than axe and alot of the stuff i have worked on is very optimized...so take my thoughts with a grain of salt i havent used axe parser in ages
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