Minecraft – Why doesn’t the mob grinder work

Place redstone torches on north walls. Redstone is quite easy to find deep underground and not required for much else.

Punch the ground directly beneath you. The break pattern is always the same relative to north.

Cheaper than torches, inlay the right-hand side of the floor with a dirt block every three squares. Build wide main corridors which you can follow back when you find one.

Grow a tree farm. Use the wood to make plenty of signs.

Design each area with its own character, so you can recognise them. Identical corridors are a good way to get lost. Place occasional markers, such as sand or wood.

Dig arrows into the wall pointing toward the nearest familiar spot. You can fill the arrow with dirt for extra visibility.

Create staircases upward occasionally. At the top, use excess stone to build a hut with a door and an observation tower. Use this to travel back to your shelter by aboveground when completely lost. Style your observation towers differently to use them as landmarks and build cobblestone roads between them.

First, take note of some information about light-emitting blocks from the Minecraft wiki:

• Torches have a light level of 14, while glowstone has a slightly higher light level of 15.
• The light emitted decreases by one for each square of distance from the light source.

This means that if you wanted to light up a horizontal line of blocks such that the light level was 8 or higher everywhere on the line (to prevent most hostile mob spawning), you could place torches along the line with 12 blocks between them, or glowstone blocks along the line with 14 blocks between them.

Now, moving vertically will decrease the amount of light as well, also by one for each block moved. This would mean that if you moved 3 blocks horizontally, then 3 blocks vertically from a torch, the light level will drop by 6 to a value of 8. So, you could just count the number of blocks you have moved both horizontally and vertically from a source to figure out what the light level has dropped to and when you need to place another light source. I believe once you reach a count of N-1 blocks from the light source (where N is the light level of the source) is when you should place another one.

A potentially easier alternative to counting is to use the debug screen (press F3) to track light levels. This will show you a bunch of stats, like so:

The number to pay attention to is the one I circled labeled "bl", which stands for block light. This is the light level due to sources other than the sun and the moon as measured at your head level. This means that if you place a torch on the ground, then stand in the same spot, you will get bl = 13, since your head is one block above the light source.

Using this may make it easier for you to lay out your light sources and to check where you may have some dark spots. I use it often inside my structures to make sure I have lit them up appropriately.