Eh, I guess I toss out one of my favorite DS games as a break from my previous Steam recommendations, so Retro Game Challenge 2, the fan translation of GameCenter CX: Arino no Chōsenjō 2. This actually may get downvoted a fair bit, because the Game Center CX show that inspired the game has a dedicated cult following in the United States and Retro Game Challenge 2 has been played by some fairly big streamers.
Anyway on to the game itself. Retro Game Challenge 2 is a collection of NES and SNES styled mini games loosely bound together by a fairly non-nonsensical meta plot and a ton of nostalgia. You're assigned "challenges" for the various games that you have to beat, think NES Remix if you've played that, it's actually from the same developer. But not only that there's a ton of nostalgic little touches, all the mini-games have in game "manuals" to read, there are also in game "gaming magazines" that offer tips and tricks for the games you play, as well as hinting about "up-coming" games. There's also a "daily challenge" which is a... well challenge that is issued daily, with difficulty that ramps up as you beat them.
The best part of the whole game/micro games is that you can freely play them after they've been unlocked. None of the NES Remix's "We've got the whole game here, but you can't do anything but the challenges" bullshit. You want to play though the entirety of the ten-ish hour NES styled JRPG? Go for it. Indieszero also included some "challenge mode" versions of games from the first Retro Game Challenge game.
Anyway, as the wall of text may have clued you in, I really like this game.
We need to do some MRI scans or something so see if the brain damage is detectable once you pass one billion dollars.