The skill tree is so flashy that it's almost impossible to actually get information out of it. Way too decorated to be legible, though I do see what you're going for, it's just... I dunno, difficult to read, especially as someone with a vision issue. Also, the presence of iron at the start of the level means iron is infinite with basically no cost; you can just start a level, click the iron, then leave. There's no point to having it as a mechanic in the game, because there's no scarcity.