Seeing as this is a modding forum, I had to include this game. It seems like it's getting pretty popular. Large fan base and a modding website with an ungodly amount of mods for the game, which are easy to install as well! It's a little space-trading/action sim called Transcendence.

The game is huge! The base game includes 3 galaxies and around 8-12 star systems in each one. A relative storyline to follow, a whole horde of items and different ships, I find the game truly amazing. Mind you, the game is 2D, but excellent graphics for a 2-dimensional game. They've recently released a few DLC packs for the game and they're on the way to getting the Greenlight on Steam.

It is worth noting that if you do download a few 3rd party mods (anything from xelerus.de) your game progress won't be recorded on the website's leaderboards. Some of the mods are spectacular though! Almost 200 playable ships, enable NPCs to use a wider variety of starships, modify in-game graphics, add a countless amount of new items, a mod that adds weapon and armor workshops to create your own items from parts that you've salvaged, even FURTHER increasing the item count... Why am I still typing? Go check it out already!!

Transcendence Home Page
https://transcendence.kronosaur.com/

Transcendence Modding Community
https://xelerus.de/

Oh, and the game is completely portable.

You're welcome