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This example shows how to rotate a game object to look at the mouse cursor. It reads the mouse position in on_input and uses the mathematical function math.atan2(x, y) to calculate the angle between the ray to the point to look at and the positive x-axis. This angle is used to set the rotation of the game object to always look at the mouse position.
If you want to play with these examples, you can get the project on Github.
Do you want to see more examples? Why not write a few yourself and submit a pull request? We love contributions.