what other bit? And yes, to make something explode into flames on contact with NEUT Put this code: if(t==PT_BOOM) { for(nx=-1; nx<2; nx++) for(ny=-1; ny<2; ny++) if(x+nx>=0 && y+ny>0 && x+nx<XRES && y+ny<YRES && (nx || ny)) { r = pmap[y+ny][x+nx]; if((r>>8)>=NPART || !r) continue; { if((r&0xFF)==PT_NEUT { parts[r>>8].type=FIRE; pv[x/CELL][y/CELL]+=5.0f } } } } PT_BOOM being the explosive Also set explosivity and flammability high in powder.h