**I’m working on a falling sand game in python and I’ve noticed two very strange glitches, the first is that the materials that shift left or right randomly, like gas or water, seem to prefer to move on one side and seem to behave differently and spread out more to the left, this is despite the fact that I used the random choice function to determine the direction. The second is, for some reason the gas when it is allowed to move more than one space to the left or right at a time can go beyond the bounds of the screen despite such things being accounted for. If anyone has experience with these types of games and knows what’s going on, it would be greatly appreciated.**

```
def xshift(arr,m,npos,ystep,x,y):
randmove = random.choice([m.spread,-m.spread])
if randmove >= 0: xstep = 1
else: xstep = -1
if xstep+x < 0 or xstep+x >= len(arr[0]):
randmove = -randmove
xstep = -xstep
elif arr[y][xstep+x] != "":
if arr[y][xstep+x].dense > m.dense:
randmove = -randmove
xstep = -xstep
for xmove in range(abs(randmove)):
if npos[1]+xstep < len(arr[0]) and npos[1]+xstep >= 0:
if arr[y][npos[1]+xstep] == "":
if type(m) == Dust:
if (arr[npos[0]][npos[1]+xstep] == "") or (arr[npos[0]][npos[1]+xstep]).dense < m.dense:
npos[1] += xstep
npos[0] += ystep
else:
npos[1] += xstep
elif (arr[y][npos[1]+xstep]).dense < m.dense:
if type(m) == Dust:
if (arr[y+ystep][x+xmove+xstep] == "") or (arr[y+ystep][x+xmove+xstep]).dense < m.dense:
npos[1] += xstep
npos[0] += ystep
else:
npos[1] += xstep
return npos
```