   Side-scroller shoot-em-up questions.
  I''ve started work on a 2d side scrolling shooter. Along the lines of Gunstar Heroes, Contra.....On a previous platform game I made, I used a bitmask approach for the tiles, ie.#define TOP_SOLID1#define BOTTOM_SOLID2#define RIGHT_SOLID4#define LEFT_SOLID8and you check for a collision in the tiles around the player''s position.I was wondering do the above games use this type of approach(I haven''t played them in years) or are platforms representedas rectangles that you check for collisions against.Also, using the bitmasking approach, what is the best method for collision checking with a sprite that''s bigger than the tiles. Say:Tile size = 32Player width  = 64Player height = 96All the previous posts I''ve read say get the players position and check the tiles around them.Would this mean checking against 3 horizontal tiles and 4 vertical tiles?Oh, and I was considering using function pointers so the player would have a different update function depending on their current action, ie.action = walking_left(); action = jumping_right(); Is this a good idea? 
  Treat the movable stuff (players, badies, projectiles) as sprites rather than tiles, that have an position and a rectangle that define their collision area. You then have to check in which tiles each side of the rectangle is going to pass through while moving, and do your collision checks between that line and the tiles.It''s possible to simplify things a bit by only checking the lines that face the velocity vector. That way you only check two lines against the tiles, at most. ;  So, you''re saying: Trace a line from each edge to the another edge and check the tiles that line intersects. I suppose that would fix the problem of collisions for larger sprites. 