Press W,S,A,D to move

Listen to the starting tile to count how many beeps are there, those are the exact amount of 'down' moves ('S' key) you need to unlock the portal to the next level. If you missed the count you can always go back to the starting tile and it will repeat it

You can exceed the given amount of 'down' moves since the count resets after you reach it, the end portal also resets after you exceed it, so calculate your steps!

There are also teleportation systems which can always be accessed, and enemies which spawn every 3 'down' moves

Basically, you need to move strategically while counting the downs.