You can start working on a new scene by using the available template when creating a scene from File/New Scene.

This scene contains the minimum elements for the game to work: HECommon and a FixedCamera.

https://lh4.googleusercontent.com/WbSjNPf_ZDmPswrfFEaSwDANevHho5q5zpnAkoBCyf7fkqoFMTo-eUpMFTmTyPT-1NDSBxg9e2UNIUicrHd2FhDN6ZWvB1Cvm6va6ULnUNvcVVt54JkLlW4C5I-5qsVnk67PzvHgNucLfkyLp5CRL4dVhxDEfabURsy640DRK8gadkzRqLI30ReH