Sometimes the ball will bounce as if it collided with the mouse when it did not. I believed this to be a result of being at a high velocity, though I've now seen it at relatively low velocity as well. The ball also does not seem to reliably collide with the mouse except when the mouse it below it, and I've encountered the ball clinging to the mouse with a bit of luck, where the mouse is inside the ball and it follows the mouse for a time. This is probably because checking collision in multiple directions is rather difficult.
A collision is whenever the mouse's position is within the bounds of the ball. The direction of the collision is dependent upon the relative velocities of the ball to the mouse or the mouse to the ball. For one dimension, if your velocity is in the same direction for both the ball and the mouse when you collide, the faster object will be striking the slower object on the side facing the faster object. So if your mouse is moving faster than your ball and both are moving to the right, the mouse will strike the left side of the ball and should impart rightward momentum. Similarly, if the ball is faster and both are moving to the right, the ball will strike the left side of the mouse, but since you probably don't want to impart momentum to the mouse on collision, you can just treat this as the ball having been hit on the right side. If the two objects are moving in opposite directions, the impact for each object will be on the side the object was moving. So if the ball is moving the left and the mouse to the right, the ball got hit on the left side and should gain rightward momentum. All of these examples function the same in the up and down dimension, simply swap right for up and left for down, so just have the program check for both dimensions. But there's an issue, you can't easily get a velocity for the mouse. To fix this, record a position for the mouse, then find the difference of that position and the position from the previous iteration of the program's main loop, which will serve as a rough estimate of an instantaneous velocity. Congratulations, you've now approximated calculus with a video game. And of course, the sign of that difference will tell you the direction of motion just as it would on the ball's velocity. With an approximation of the mouse's velocity, you can also use that to better model the reaction of the ball to being struck.
There is also the special case of when one of the objects is not moving. If the mouse is not moving and the ball strikes it, the ball should reflect. If the ball is not moving and the mouse strikes it, the ball should go in the direction of the mouse's motion. This should be done by dimension, not overall. So if the ball is moving in one dimension but not the other, it should act as if it was hit while moving for the dimension it is moving in and act as if it was hit while stationary for the other dimension.
Of course, I notice you're using Construct 2, so I still don't know what kind of control you have over that kind of thing.
