It’s not pretty, it’s not fancy, but I did it in 20 minutes and it works.
Click a level, that sets a filter check. CLICK ME represents whatever is used to beat the levels. Clicking sends you back to the menu. If you beat the level, it upgrades the filter requirement, and the next level unlocks. You can’t unlock new levels from old levels. RESET wipes the memory. You can repeat this in your game if you want.
Replace CLICK ME with a door, wall, key, or whatever you want to use to go beat the level.
Replace the Next Level (2) with the corresponding level to the button.
Replace the graphics with something nicer.
Congratulations, you now have a menu level unlock system in your game.
Remember to have MEMORY and CLICK ME on EVERY SINGLE LEVEL.