Tank Land is a game inspired by Battle City by Namco(Now Bandai Namco) where you have to defend your 4 flags from the endless wave of enemies, there are also powerups to help along, the objective is to survive as many stages as you can, if you lose all your 4 flags, your game is over, want to hear more data? Go here for help.
The PICO-8 version is the original. It is arguably easier than the TIC-80 one since due to the PICO-8's token limit, the AI for enemies and allies are stupid as hell, and the missile sprites are wrong, the TIC-80 version fixes all of that, polishes the animation of jets, etc, it also has better soundtrack, which is the official one.