Terra 2222 is a completely open-source & vanilla JavaScript game. The entire project has been built in 4 days as part of a school project.
The game itself is a space-based shooter and features working collisions, enemies, a built wiki with documentation about the world and the controls.
Terra 2222 also packs a custom shop with an economic system and buyable perks such as custom spaceships, custom ammo or upgrades for your vessel.