A special state of calm, relaxation, and completeness that was achieved from a particular aspect or portion of a game.

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I'll name a few:

- EarthBound: Insanse stat increase after beating the Mani Mani Statue as a result of cleansing the evil from your consciousness

- Wii Sports: Getting into the calm zone of the tennis minigame where you have to hit the target on the wall with a breakable backdrop

- WindWaker: When Hyrule is drowned in water at the end rather than saved by the triforce, highlighting the importance of "letting go"

Journey - The whole game in life in general.
Abzu - The whole game in life in general.

I most associate this with DDR. Where the steps keep coming faster and faster but somehow I'm keeping up without even realizing it. That was ages ago when I could still play.

A more recent one may have more to do with being, "under the influence."

I was off work and decided to spend the day mixing myself cocktails and replaying Metal Gear Solid 2. I had a good buzz going by the Plant chapter. By the time I stopped to think about how things were going, I was already at the Emma escort part and I hadn't been spotted at all. That was pretty neat.

I wanted to say Life is Strange, but no that wasn't Zen at all, it was crippling depression.

Any porn games

Axelay on the SNES
Ori on Xbox One
Any version of Street Fighter 2

I'd just enter a trance of reflexes and amazing things would happen. I'd look back at footage of myself playing them and say to myself, "Damn. I'm pretty good."

You don't get that feeling in games that hold your hand. I imagine a lot of people get that feeling from Call of Duty but not me. I suck at that series!

Overwatch - Playing as Zenyatta

It was definitely when I was playing Final Fantasy X with a friend, but he had to go home for a few hours. So, I just paused the game to wait for him. The song that was on was Besaid. I loved that song so much, I just calmly listened to it while waiting for him. That was definitely the day it became my favorite game.

When you get to the entrance of the Temple of Time in Twilight Princess.

Every Dive to the Heart section in the Kingdom Hearts series.

The Greenhouse section in The Swapper.

Skytown, Elysia from Metroid Prime 3 (well, except for the lab. Fuck the lab. Burn that place).

Playing Weezer's Undone (The Sweater Song) on Audiosurf.

The first half is so calm and easy.  It picks up around the 2 minute mark and then when it amps up again at the 4 minute mark, my whole world is brightly colored blocks.  That last minute seems to last forever.

In the Fallout 4 Nuka World DLC, there is a raider faction known as The Pack.  They wear brightly colored clothing and act like hipsters pretending to be animals.  There are also cat NPCs.

Once, when I was attacking a group of enemies with The Pack as my allies, I saw one of them split off.  Puzzled, I jumped on a wall to get a better view.  From there, I simply watched in mute fascination as this particular member of The Pack chased after a cat while howling and waving a pink baseball bat with saw blades attached.  They eventually disappeared into the horizon but, before that, I felt like I finally understood life in general.