He shoots*, he scores
* but only asteroids and mines.
Collision handling's going to be a bit different for Draconian as it's not feasible to check against all 150 sprites. One handy thing I can take advantage of is how the asteroids and mines are positioned. The screen's divided into horizontal bands that are 32 pixels tall. 4 stationary objects (combination of asteroids and mines) can appear in each band, and they're positioned so they never straddle multiple bands. Sprites 22-25 are in the first band, 26-29 are in the second band and so on.
Based on that knowledge I can limit the collision checks for shots by doing the following:
#define PLAYER_SPRITE 8 #define FORMATION_SPRITE 9 #define FIRST_STATIONARY_SPRITE 22 #define STATIONARY_DENSITY 4 for(i=0;i<4;i++) { for(j=0;j<8;j++) { // not yet written, player shots and station collisions } for(j=FORMATION_SPRITE;j<FIRST_STATIONARY_SPRITE;j++) { // not yet written, player shots and enemy ship collisions } height = shot_height[i] start = ((shot_y / 32) * STATIONARY_DENSITY) + FIRST_STATIONARY_SPRITE end = (((shot_y + height) / 32) * STATIONARY_DENSITY) + FIRST_STATIONARY_SPRITE + STATIONARY_DENSITY for(j=start;j<end;j++) { if (Collision(shot_shape, shot_x, shot_y, j) { // process collisions } } }
So instead of checking for collisions against 150 sprites I only have to check against 25 or 29 sprites. That's 8 stations + 13 enemy ships + either 4 or 8 stationary objects (depends if the shot straddles 2 zones).
Also added some temporary sound effects (borrowed from Space Rocks) and revised ship graphics (the 45° images).
ROM
Source
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