Just do all the web games on my profile. But for your own sanity, don't run Kirbo.
Have you checked out the games in the advertisement thread? Many of them fit your parameters.
One of the things I've posted in that thread is a general call for people to check out pico8 games. All but 3 or 4 of those are doable in under 20 minutes, and they all have free web versions. That'll give you a few dozen to choose from.
If you want fairly quick/easy to complete pico-8 games, I'd suggest Shelled Shinobi, Yarn, willo, Terry the Turtle's Big Adventure, Winterwood, and the any% w/mistakes in Santa Panic.
If you want more of a challenge, check out Ninja Cat & Grippy.
Edit: Note that the pico-8 console allows developers to release their games on Linux by default, so many pico-8 games have Linux versions as well as web versions (often but not always free).
