Slabs and stairs are meant to be only partially transparent. This means that they should block light from passing through. This is how they function on Java. On Bedrock, however, they act as fully transparent, allowing light to pass right through. This causes visual glitches with some slabs and stairs while also allowing light into places it shouldn't be able to reach.

Steps to Reproduce:

1. Build some structure or wall with light on one side and no light on the other
2. Break a block in the wall, allowing light through, and replace it with stairs or a slab (slabs only work in the ceiling or on the floor)
3. Expected Result: The slab or stair blocks the light from passing through
4. Actual Result: The slab or stair does not block the light