Part 2 of this guide from Emanuele Feronato: "Here we go with the second step of Perfect Square! game. In first step we saw how to create the basic prototype of the game in only 100 lines, this time we are going to add only 30 more lines but we will feature level progression and the main GUI.
In games like Perfect Square!, as well as Circle Path, you don’t actually progress through levels: you just have to make a successful move in level 1 – in this case make the square fall in its place – then you advance to level 2 where you have to make two successful moves, reaching level three where you have to make three successful moves and so on."