Starheim is a free to play spaceship piloting looter shooter MMO with ship progression set in a universe based on Norse mythology in early access for PC and Android (Google Play).

Combat:

The game focuses heavily on ship to ship combat, allowing players to blow up NPC ships en mass and collect the loot they drop, or fight other players.

The main idea is to simplify the spaceship piloting mechanic seen in other big space titles like Eve or Elite Dangerous by locking ships and bullets so everything is on a flat plane. Not having to deal with anything moving up and down makes it possible to control a very fast moving ship, dodge bullets, and warp around like not usually seen in MMO space games.
A major decision was made early in development to not feature any kind of "Heat seeking missile" type weapons, meaning you have to actually point your ship at a target to hit them. I've never really cared for the "Locking on and firing a missile and waiting to see if it hits" type of space combat, even if it is more realistic.
Boss fights are designed to be taken on by a party of at least 2 players, and party members share EXP, encouraging team play.

Physics:

Ships are all driven by real physics, meaning when you push the forward button, your ship gets pushed forward with realistic thrust, and momentum is maintained until you press back to activate the reverse thrusters to slow down. This can be challenging to get the hang of, but it does make for a more realistic spaceship pilioting experience, and opens up ways for players to play around with the physics.
Slamming into another player will effect their movement or send them spinning off, instead of you ship just bouncing off.
Asteroids are driven by real physics too, allowing you to shoot them to launch them at people or NPC enemies.
All ships come equiped with a Tractor Beam, which creates a gravity well in front of the ship that attracts asteroids and NPC ships, allowing you to "grab" an asteroid and carry it around with you and shoot it to launch it at someone on demand.

Open PvP:

While fun combat is always important, the primary goal with the game was to create a sandbox where players can interact with eachother.
A lot of inspiration was taken from oldschool MMOs where you could just get on and mess around with random people in an open PvP enviroment, and the mechanics are as open as possible to allow players the freedom to play however they like.
Most of the world is Open PvP, with the ability to set it to "Peace" or "PK" mode.
Enforcer ships protect high traffic areas like upgrade centers, and will attack PKers on sight.
Death isn't super punishing unless you haven't put stuff in the bank, so it's all in good fun.
PKers (Player Killers) get 10 PKPoints when they kill another player, and getting 30+ PKPoints makes a player redname, where they can drop their equipped modules if they die, upping the stakes for attacking other players.

Factions:

The game has a Faction system that allows peoples to create or join a faction with other players.
Later the faction system will be used for a faction vs faction PvP event, pitting the followers of dark gods like Loki against the gods of order like Thor.

Making the strongest ship you can:

Players can build ships of several different classes including:
Fighters (Speed Focus)
Destroyers (Damage Focus)
Frigates (Survivability Focus)
Artillery Cruisers (Heavy Weapon Focus, think big railgun)
Dreadnought (Good damage and survivability but slower and a bigger target)

Modules to add additional offensive or defensive capabilities can also be bought or looted and equipped to ships to increase their stats.
Ships and Modules have an upgrade system similar to land-based MMORPGs, with stats that go up to Legendary, +9, 2 Sockets.
Since it's based on Norse mythology, we had to make the objects that go into sockets Viking Runes. These runes grant various stat inceases or effects like boosting EXP gained.

Elements:

The game is heavily element based, each weapon being able to change between 8 different elements, changing the visual of the projectile and changing the type of damage it does.
Nearly every ship has an element based energy shield that needs to be taken down before damage can be dealt to the ship's Hull HP.
Hitting a shield with an element that counters it does 50% more damage, for example hitting an Ice shield with Fire element.
Hitting a shield that counters the weapon deals reduced damage, for example hitting an Earth shield with a Lightning bullet.
Countering NPC shields with an opposing element increases their drop rates by 50%.

The game can be played with a Mouse and Keyboard, Touch Screen, and partially with a Controller (Mouse and Keyboard still needed to navigate the UI, Controller to control the ship).
It runs well on Steam Deck even in the early access version, and has an input mode specifically tailored to Steam Deck, but some functionality may always require the touch screen such as dragging items from one inventory to another. Steam Deck is kind of the perfect type of device to play it on since it's the kind of casual experience Steam Deck was built for, so good Steam Deck compatibility is high priority.