Game balance and increasing diversity.

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In all kinds of games, across mediums, game designers strive to create variability in gameplay, to make sure their game does not become stale. Players need options, and for many of those options to be viable, so that the players gain enjoyment from combining their options together, in creative and effective ways. An important part of this is to make sure all options really feel different, and yet all of them are valuable. If all choices are equivalent, then choosing is like selecting a piece in monopoly. If some options are always suboptimal, they might as well not be in the game. So every game designer has to realize how different their options really are, and provide a semblance of balance.

At the highest levels of 2 player strategy, there's always just a few groups of possible goals, and they apply to puzzle quest:
There's ramping, which makes it easier to use more powerful options. In MPQ, think of IM40's recharge.
There's moves that hurt the enemy. For instance, Thor's Call of the Storm.
And last, there are moves that stop the opponent from hurting you, or undo said damage. An example is in game healing.

All moves work towards at least one one of the three goals. In MPQ, many combine more than one.

So today, what is MPQ all about, at the highest levels, today? The most important thing is to win quickly. And since we care more than just about a single match, but a series of matches, we also want to not get hurt. A downed character is a minor tragedy. A hurt character means you will have to go heal.

Given this, it's pretty easy to see why Magneto/Patch is a good combination. Patch attempts to win quickly. Magneto does its best to make sure the opponent can't retaliate, because they don't even get to move. He also helps ramp patch by maximizing how many AP you can get without your opponent landing even a basic attack on you. It's not quite an old Spiderman lockdown, but it doesn't have to be. This also explains why OBW is such a powerhouse: She does a bit of damage with black, she ramps though her purple, and blue keeps you in the game, and playing for longer. We can also see why characters that don't help any of those very well are not seen much. IM40 just ramps, and badly but is bad for anything else. Ragnarok barely ramps, has no defensive capabilities, and is a weak damage dealer.

So what happens to a metagame like this is changed by, say, weakening healing between games? It changes the value of absolutely everything else.

Our biggest goal, to not get a character downed, is there just as much as before. But now getting hurt more than 15% is probably no better, as going into a fight with low HP will make it easier to lose not just that character, and not just the points in play, but get the other two characters you are bringing in out of commission. So now taking damage is just terrible.

So how do players that remain react to something like this? Well, it's easy: By putting more of a premium on not getting hurt. So any character that hurts its own team gets far worse. Anything that makes your opponent not be able to take turns gets better, way better. So a change in the rules will not necessarily lead to more characters getting used, but to more people using the few characters that lengthen your turns, stop you from taking damage and stop the opponent from moving. Hello AP generators. The other characters that get better are those that can still heal, and heal all the way. Suddenly Patch and Daken become extremely good, because they let you keep playing. They also have different colors, so they will tank a bunch. Your third character should be someone that either stops the opponent from playing, or that deals a tinykittyton of damage, all while being at a low enough level that it doesn't get hurt outside of global effects. Then, instead of healing everyone in the prologue, we can just go heal patch and daken instead. Not exactly a recipe for diversity, is it?

You can't make people play the game badly. So any major mechanics changes will just mean that a different small set of heroes will be used, unless the designers understand the roles, and how the environment surrounding the actual match 3 game affects player choices.

I could also get into why the current monetization strategy is not optimal for a userbase this small, and for a game that is 100% a competition. It should move to something more like League or Dota, but that's for another time.