SteemNova 2 is the successor of the successful SteemNova game, i.e. the open source clone of the Ogame game (browser-based, multiplayer space game). What SteemNova had was a much smaller number of bugs, open sources (SteemNova is based on 2moons code, which is licensed under BSD/MIT - so there is no need to share the code) and general fixes, which outclassed the competition.
Of course SteemNova 2 allows you to make money in Steem cryptocurrency, but if you don't have an account and don't want to make money you can continue playing with login and password or create them later.
The game is of course free ;)
Tutorials (Ogame, but it's compatibile): http://wiki.ogame.org/index.php/Tutorial:First_steps/
If the game will be popular then in 2021 I will add bitcoin support (or earlier, we will see).