Iris and the giant is an artistic, thoughtful entry into the deckbuilder genre with strong movement puzzle and good out-of-game progression based around optional challenges you can complete as you attempt to progress through the main gauntlet. You burn most cards as you play them, and running out of cards loses you the game. Your main obstacles are various mythological demons, who represent the inner struggles of the main character. They will attack you if they’re in the right position and you don’t kill them first. They tend to deal one or two points of damage, with larger damage totals tending to come from the ‘big demons,’ who also drop new powers and interesting abilities. Sometimes they wear armor, which blocks a point or two of damage. Sometimes your attacks deal multiple points of damage- usually from a power or other modifier. Speaking of your attacks, they are a big part of what makes the game feel so ‘puzzl-y’- they are highly directional and highly situational, but the decision of which cards to take was made many, many rounds ago. You must constantly balance the cards you take against the cards you spend, while the constant damage of the monsters pushes you forwards.
Its tight design and clear visual style means that everything is as clear as possible. Every card has mouseover hints, and every time you play the game it unobtrusively asks if you remember the rules. Every monster has a clear silhouette and a role. Every item has a purpose. Every twist to the game feels intentional and interesting and fair. My deaths have all been my fault. It’s brilliant!
So naturally I was thinking about dnd. In Iris, enemies sometimes have armor that blocks a point of damage. Sometimes they even are wearing helmets or something and absorb two damage. A few rare enemies block three damage.
It works well in the game. If we did something similar in DnD, it might look like this:
Light armor gives you 3 Armor Points.
Heavy armor gives you 6 Armor Points. (optional: gives you disadvantage on swim/climb/sneak/hide)
Magical armor gives +3 Armor Points.
Shields do not provide Armor Points- instead, they provide +2 AC/Defense.  Of course, shields shall be splintered.
When you take damage, you can choose to take the damage to your armor points first. Your Armor Points recover when your hit points recover. If your Armor is reduced to zero Armor Points, mark 1 Wear on that armor. Wear reduces the maximum armor point value of armor until it is repaired, patched, and/or maintained during a rest period, at a rate of -1 Wear per rest. 
 In my ideal world, attack bonus would be checked against Defense, and we would all agree that Armor Class deserves the same fate as THAC0. This is assuming that you like static armor class, of course.
 Even for a short rest, maybe you can just knock some dents out, adjust some straps, improvise a repair, whatever. The idea is that armor points are a pseudo-temporary hp and that you need to rest to get them back. But not immediately.
Some snippets of abandoned houserules:
Armor Points Value:
Light Armor is worth 1d6 armor points. Medium Armor is worth 2d6 armor points. Magical armor is +1d6 to whatever the base was. You roll your Armor Points at the beginning of each battle.
When you take damage, you can choose to take the damage to your armor points first.
When you take damage, your armor is damaged first.
Armor Point Recovery:
Your Armor Points recover during a rest, at the same rate your hit points do.
When your armor is reduced to zero Armor Points, mark 1 Broken on the armor. When there are as many Broken marks as the armor’s maximum armor point value, it gains the Broken status and provides no benefit until it is repaired.
When your armor is reduced to zero Armor Points, mark 1 Wear on the armor. Wear reduces the maximum armor point value of armor until it is repaired, patched, and maintained during a rest period.
Your Armor Points recover at the beginning of any given combat.
As long as you are wearing Heavy Armor, you have disadvantage on swimming/hiding/climbing/sneaking rolls.
As long as you have at least 1 AP, you are considered Armored. As long as you have at least 4 AP, you are considered Heavily Armored. As long as you are Heavily Armored you have disad…
As long as you are Armored, you reduce incoming damage by 1. As long as you have at least 4 AP, you reduce incoming damage by 2.