Grid the landscape, and shortcircuit checks on the collision array if there are no nearby checked in collisions to be collided with. This is a big win for fire's ammoshove in particular. Also add a +2 that seemed missing in the check, and update fire accordingly.
/*
** $Id: lstring.h,v 1.43.1.1 2007/12/27 13:02:25 roberto Exp $
** String table (keep all strings handled by Lua)
** See Copyright Notice in lua.h
*/
#ifndef lstring_h
#define lstring_h
#include "lgc.h"
#include "lobject.h"
#include "lstate.h"
#define sizestring(s) (sizeof(union TString)+((s)->len+1)*sizeof(char))
#define sizeudata(u) (sizeof(union Udata)+(u)->len)
#define luaS_new(L, s) (luaS_newlstr(L, s, strlen(s)))
#define luaS_newliteral(L, s) (luaS_newlstr(L, "" s, \
(sizeof(s)/sizeof(char))-1))
#define luaS_fix(s) l_setbit((s)->tsv.marked, FIXEDBIT)
LUAI_FUNC void luaS_resize (lua_State *L, int newsize);
LUAI_FUNC Udata *luaS_newudata (lua_State *L, size_t s, Table *e);
LUAI_FUNC TString *luaS_newlstr (lua_State *L, const char *str, size_t l);
#endif