I have been using Super Math World (https://supermathworld.com/) in my grade 5 class for the last two years. It is a great example of immersive game-based learning for younger learners. I first came across it when exploring https://www.youcubed.org/ and Jo Boaler, which is an amazing website. I use it for problem-based whole group lessons, as well as with small groups to reinforce specific concepts. I have kids use small white boards to solve problems symbolically and then test their thinking in the games 3D environment.