Easiest way to think of this is to give each body a power-of-two number
player=1
dumb=2
edge=4
barrier=8
bonus=16
tile=32
This will be their CategoryBitMask
Now to calculate the CollisionBitMask
You want player to collide with dumb, edge and bonus
so the CollisionBitMask is 2 + 4 + 16 = 22.
dumb can collide with dumb edge and barrier
so the CollisionBitMask is 2 + 4 + 8 = 14
barrier collides with dumb
so the collisionBitMask = 2
bonus collides with player
so the collisionBitMask = 1
tile collides with nothing
so the CollisionBitMask = 0
Simple!
The way to works is because the numbers are powers of two, they represent a bit-pattern
00000001 = 1
00000010 = 2
00000100 = 4
00001000 = 8
00010000 = 16
So the collisionBitMask for player (22) is
00010110 = 22
Now, when you logically AND to binary numbers, the result is a 0 in every position except where BOTH numbers have a 1
so
0001 & 0001 = 0001
0010 & 0001 = 0000
0011 & 0001 = 0001
So, if I take the player bitmask (22) and AND with barrier category (8)
00010110 & 00001000 = 00000000 - which is zero - so they do not collide
AND with the Edge category (4)
00010110 & 00000100 = 00000100 - which is not zero, so they do collide.