Whenever Nintendo posts a new video game, there is usually a free demo that will also launch on Nintendo Switch Eshop. It is completely accident when the company actually does so. Sometimes they will announce the demo before the full game is starting and the second time they wait after that. They also like to do the demonstration of the game available without any pre -warning.
For example, before tonight, Nintendo decided to suddenly let the free demo for Donkey Kong Country Returns HD. The game was officially published on Nintendo Switch almost a month ago, January 16th. You can find it on ESHOP Nintendo Switch. The post on social networks that transfers the news can be seen down.
