I found a notepad with some of my very first card designs on it. Here they are, without any changes.

This eventually became Eye of Harmony.

There are so many things wrong with this, I don't even know where to start. It's funny: people screwing up WUBRG is one of my big pet peeves now.

Haha. I was looking through my cards on here, and it just seems like the ones I designed a year ago are so bad. The worst part of this one, for me, anyway, is the mana cost on a land.

As silly as this is, it seems rather reasonable. There probably is design room for mana cost on lands... the rule book would need quite a few paragraphs up updating to do it, though...

It seems like it would make lands into spells, which means a whole lot of changes and interactions that I, personally, don't want to see.

Not really. You could just have something like "As an additional cost to playing this land, spend X mana". But I do understand why, like, 95% of the Magic playing community would hate that.