I was playing Miner Cat 4, and I came across the bottom of the world. I just thought it was just another layer for me to get more valuable ores, until I realized the blocks were unbreakable. Then, I dug around until I found out I got to the bottom of the world! I then made this screenshot (left). When you reach the crimson layer that can't be mined instantly with even the strongest pickaxe or auto-miners, you are close to the bottom. It might take real time hours, days, or even weeks to get to the bottom.
Game is here if you want to play it: https://scratch.mit.edu/projects/487580583 I used the developer's save to get here faster, but it still took quite a bit of time to find the bottom. Plus, I even died once because of a zombie.
