Duel of the Arcana for people who understand MtG, from first principles

Broadly, DotA is designed for people whose favorite aspect of MtG is the stack. In DotA, the stack is the only zone that both players put cards in. It is always visible, and big, in the UI even while empty.

from Noah, my friend who designed it:

Based on the above information, we will now derive the rules of the game from first principles.

Alright so what do you need to have a good MtG-esque stackful experience? Well you need a deck, hand, discard, for sure. You need mana that can be exhausted and refreshed (but you certainly don't need dedicated mana cards and resultant variance). And of course you need a stack. Great!

Oh, and you'd keep HP, hard to have a generic victory condition simpler than “make this number go down”.

You don't need turn phases -- while “drawing” and “untapping” are meaningful here, “it's my/your main phase” is kind of meaningless if everything is at instant speed. Also, nobody should be saying stuff like “just making a note that I want to do something at the beginning of your end step”, and the UI for such a concept is horrid.

You definitely don't need creatures, nor tokens¹. Disgusting.

You probably want some activated abilities since those are cool. So we can have artifacts (relics)². After all, having some forms of progress/game state outside the stack does serve to add variety to the stack-based experiences and can serve to create interesting stakes for the on-stack drama. So we can have Enchantment spells as well for persistent effects.³

Oh, and you definitely want Storm. Of course.

Speed

You also want to have some spells that are “slow” and others that are “fast”. In MtG there's sorceries vs instants (great names...), but we don't have turn phases, so we really just care about which spells can respond to which. Enter what is probably DotA's most interesting novel mechanic, speed:

When evaluating cards, I think speed is the component newer players will most overlook at first. I think knowing what outspeeds what is one of the biggest learning curves, but in practice it ends up being incredibly interesting and I really underrated this mechanic at first.

I thought it would just be “what beats what”, but it actually has a lot of implications for how you chain together your own spells (something you typically want to do, for the sake of maximizing action efficiency). You often wish spells were slower! (relative to other spells in your hand -- if you could make all of your spells faster that is in fact just better)

colors

well everyone loves the color system so you obviously have colors. In fact you will have much more than 5 colors since that would be much cooler -- if you think about it, there should really be 8.

making mana

everyone hates lands. but colored costs are great. if you just do things like Hearthstone or Legends of Runeterra, you don't have colored costs. thinking about which lands to tap in order to keep what cards open... is cool. picking which land to destroy based on what you don't want your opponent to be able to cast, is cool. what to do?

okay how about this: any card can be a land if you play it as a land, and in order to constrain color usage, you just have to decide up front what colored land it will be.

so you have all the gameplay of the end-state (having differently-colored lands in play) and none of the drama regarding what lands you're able to draw. You also get new very interesting gameplay around which cards you want to keep in your hand so you can cast them, which ends up mattering a lot!

This is just a much better design for the exact same thing! MtG would probably just be better if they did this! Wow!

(It also impacts deckbuilding, since you can have cards that are more situational but never dead, which ends up providing the same metagame counterplay stuff as sideboarding, without having sideboarding, which is IMO cooler.)

wait, no turn phases?

Right, so if there's no turn phases, when do you draw cards? when do you untap? when do you make mana?

Your turn can be any one of those things. Fascinating! You never had to consider before whether you'd rather draw or untap next, but now you do, and it ends up being a really interesting decision. I just think this is extremely elegant and somehow creates so much more gameplay and complexity than phased turns while also being much simpler and cleaner.

You have now derived DotA from first principles. Great work!

in sum