Demo: Press "Ideal 3 State" and then "Start."
This is a Turing machine simulator, specifically for the n-state Busy Beaver problem. The ruleset at the top directs how the machine works. The red lines indicate the current state of the machine. A is the default state, and the bit indicates the number the machine is currently reading (above the other red line). The 3-bit rule specifies what happens in the next iteration: the first bit is what the machine will write, the second bit tells you the direction the tape will move in, and the third bit tells you the next state. The goal is to write the rules such that your program eventually halts and outputs the most 1s possible.
You may want to try making your own ruleset. Just click the appropriate rule and it will cycle through the options. You can also change the number of states, although the problem gets exponentially harder!