Creating a fully functional 3D game like Stumble Guys would require a significant amount of time, resources, and expertise. However, I can provide you with an example of a simple game implementation as a starting point. Keep in mind that this code is just a basic demonstration and not a full-fledged game like Stumble Guys. Here's an example of a simple game implemented using HTML, JavaScript, and CSS:
This code sets up a basic game canvas and allows the player to control a rectangle (representing the player character) using the left and right arrow keys. The game loop continuously updates the game area, clears the canvas, moves the player, and redraws the player on the canvas. Again, please note that this is a very basic example and would require significant enhancements and additions to match the complexity and features of a game like Stumble Guys.