Humble Plug In (and Play!) is a game software bundle.

$1 Level

• NeuroVoider ($14, not tested with Catalina) - Twin-stick shooter RPG.
• Hover ($20, 32-bit) - Science fiction parkour game.
• Anarcute ($15, Windows) - Riot simulator where the rioters are cute animal beings.

$6 Level

• Sundered: Eldritch Edition ($20) - Side-scrolling shooter with hand drawn art.
• Plane Mechanic Simulator ($12, Windows) - You're a British airplane mechanic during the Battle of Britain
• Epistory - Typing Chronicles ($15, Owned) - An adventure game set in an origami world.
• Chroma Squad ($15, Owned) - Tactical RPG where you are actors in a Power Rangers ripoff tv show.
• Dead in Vinland ($20) - Control a Viking family in a new world, balancing relationships and building a colony.

$10 Level

• TT Isle of Man: Ride on the Edge ($40, Windows) - Motorcycle racing game set on the 37.73 mile Snaefell Mountain course.
• Sigma Theory: Global Cold War ($10, Owned) - Turn-based scientific research and espionage game.
• Tennis World Tour ($50, Windows) - Play as one of 30 real-world players.
• WRC 8 FIA World Rally Championship ($40, Windows) - Car racing game.

I own more of these than I expected. It looks like at the $6 level I get two $20 games. Dead in Vinland sounds kind of interesting so might be worth it.