char collide(int x, int y, char level[], char tile);
char collide_spike(int x, int y, char level[]);
char collide_solid(int x, int y, char level[], char polarity,
	char test_semi_solid);
char collide_point(int x, int y, char level[], char tile);
char collide_and_erase(int x, int y, char level[], char tile);