"Cube World" by Picroma does have a demo, but it is not playable. It is designed only to test the hardware capabilities of computers to ensure they can run the game before it is purchased and installed.
The "Cube World Mini Demo" simply shows a rotating landscape. The computer is capable of running the game if the background rotates smoothly and a logo and text are visible. Picroma notes that laptops with integrated Intel graphics chips tend to have problems running the game. If the demo does not start, the company recommends installing the latest DirectX End-User Runtime, which can be obtained for free from Microsoft.