[ we make science jokes, periodically ]

The Minecraft world is ginormous and it's pretty easy to get lost. There's a fix for that! With this Crumb, you'll leave a trail of crumbs wherever you go so you'll never be lost again! 

Step 1
Delete the on start  and on chat command blocks.

Step 2
Add an on player walk block

Step 3
Add a place block inside the on player walk block. 
Pick a block to trail.
Change the position parameter to read ~0 ~0 ~-1

Here's something on parameters:

You can finish here,
or if you don't want a block with every step, here's what you can do: 

Step 4 - not really a step, but read this!
What if you don't want a block behind your every step? Here's a way to change it! You can pick a random number between 0 and 3. 

Step 5
Pull the place block out of the on player walk block.

Place an if just inside the on player walk block and put the place back inside.

Step 6
Put a 0=0 block inside the if block.

Put a pick random block and place it inside one of the 0s of the 0=0 block.

Change the pick random block to pick a random number 0 and 3.

Chance the other 0 to a number from 0-3. We chose 1. 

And you're done!