Polish 11 Bit Studio's popular This War of Mine is on sale on Steam. You get the full game, season pass and DLC's for 18,57€, roughly $20. Not only that, the developers will use 100% of the income for the next 7 days to help victims in Ukraine.
There's really no questions to be asked here. Buy the game and show your support, not only to the Ukraine people but also to a developer and their game which is very much about what is going on in the world right now.
"For the next seven days, all profits from This War of Mine, all its DLSs, on all stores and all platforms will go to a special fund. A week from now, this money will be donated to the Ukrainian Red Cross to directly support victims of war in Ukraine."