Surviving Mars Deluxe Edition is currently FREE on Humble Bundle if you sign up for their newsletter (basically email news). You don't have to pay anything. Just login/create and account and the game is yours!

As of writing this you have 2 days and 15 hours to claim!

https://www.humblebundle.com/store/surviving-mars-deluxe-edition-free-game?hmb_source=humble_home&hmb_medium=product_tile&hmb_campaign=mosaic_section_3_layout_index_2_layout_type_carousel_tile_index_1_c_freegame_2021_storetile_survivingmarsdeluxe