I totally forgot about mapping arrow keys as an alternative to WSAD. I will update the game after the voting period ends.
About the missing tutorial for boxes.. At the beginning I just made springs, spikes, ice floor and tar floor, then created few levels. Few hours later I realised "this is boring". So I added next stuff, few levels later I got bored again, and added something new again. That's why there is no tutorial for buttons, platforms, doors and boxes. On my checklist "make tutorial" was already ticked off when I created those new mechanics.