Basic Card Mechanic

The basic card mechanic involves a number of aspects:

* Exhaustion - that cards increase their cost when you play them.
* Cooldown - that cards decrease their cost when you rest from them
* Minimum Cost - that there is a limit to how low the cost can go
* Card Upgrades - that there is an infinite number of upgrade steps you can take on each card, based on the stats of the cards:
	+ Minimum Cost, Exhaustion, and Cooldown
	+ Variables 1 and 2
	+ Initial Lifeforce

With these mechanics, I hope to have created an interesting gameplay that will hold up through an entire game. The main concerns are:

* Changing costs on cards requires you to constantly re-evaluate them.
* Eternal upgrade steps will result in overpowered cards.
* Since old cards are generally played more, they are also more upgraded. What is the incentive to buy new cards?
* Progress is slow, and the upgrade of a single stats only 1 step might feel too un-awarding in the long run.
* Is the system too mathematical in such a way that a certain upgrade path is always the optimal one?

### Triad: Cost, Exhaustion, and Cooldown

Since this is the most basic mechanic, it has to be interesting. For quite some time, I had the feeling that the upgrade path here was too mathematical and obvious: you would almost never upgrade the cost, and you would always choose exhaustion or cooldown based on which gained the greatest percentual benefit from upgrading. So if you have a card that has 3 exhaustion and only 1 cooldown, you would always upgrade cooldown, and vice versa. Although this is often the case, I have come to realize that this thinking is based on the presupposition that a card is played and rested from equally over time. If that were the case, my thinking would be correct.

But it is very seldom correct, or at least you don't want it to be. Some cards you want to be able to play every time you get them and only rest from once every now and then. In that case, the exhaustion value will be applied more often than the cooldown, which makes it more appealing to reduce that value when upgrading. Other cards have quite situational effects, which means they are naturally going to be rested from several times before being played again. In that case, increasing the cooldown might be better. The minimum cost is still very seldomly chosen, and I am thinking about increasing its upgrade to reduce the minimum cost 2 steps instead of just 1. However, the minimum cost is important to prevent the best cards from being too cheap to play. Some cards are costed at 40+ just to make sure they are not played every turn.

So, in summary, the system has turned out to not be too obvious, especially if there are other cards manipulating costs in other ways. For example, the card Hindsight reduces the cost of you last played card by 3, which is better for a card with low exhaustion than a card with high cooldown. The counterpart of that card, Patience, performs 2 actual cooldowns on a card. That is better on cards that have higher cooldown, unless it is actually wasted on those cards, since only 1 cooldown would be enough to reset the cost.

### Upgrades

So, when you're upgrading, it is not certain which parameter you want to upgrade, and that's great! The minimum cost is still very seldom chosen, so the question remains if that should be buffed. Most cards use at least one of the variables available, and that is also usually upgraded but not always from the beginning. A card with lifeforce can have its initial lifeforce upgraded, resulting in it being in play one more turn. The value of this varies greatly from card to card, but this upgrade can be awesome! The cards usually have a lifeforce of 3 from the beginning, and this is because I don't want the increase by 1 to lead to too large percentual effects. Only cards with weaker abilities should have shorter lifeforces from the beginning. The impact of increasing the lifeforce of a card in comparison to changing the cost triad of stats is that the whole card's effects are multiplied (if used).