Hey! Thanks so much for playing. Yeah you're right. Each level has two goals, one relating to the coloured blocks and then one relating to the grey (large) boxes. So the intended path is playing through each level left to right solving them using the coloured blocks, learning how to scale up and then going back through them.
I planned to put in something simple like an arrow pointing back to the previous level but it really came down to the wire with bugs and I completely forgot!
If you're interested in giving them a go as a scaled up builder you can always load the game back up and try them without having to complete level 3 again. You can always scale up if you know how to!
Thanks again for playing!