I want to have simple 45° slopes in my tile based platformer, however I just cant seem to get the algorithm down. Please take a look at the code and video, maybe I'm missing the obvious? //collisionRectangle is the collision rectangle of the player with //origin at the top left and width and height //wantedPosition is the new position the player will be set to. //this is determined elsewhere by checking the bottom center point of the players rect if(_leftSlope || _rightSlope) { //Test bottom center point var calculationPoint = new Vector2(collisionRectangle.Center.X, collisionRectangle.Bottom); //Get the collision rectangle of the tile, origin is top-left Rectangle cellRect = _tileMap.CellWorldRectangle( _tileMap.GetCellByPixel(calculationPoint)); //Calculate the new Y coordinate depending on if its a left or right slope //CellSize = 8 float newY = _leftSlope ? (calculationPoint.X % CellSize) + cellRect.Y : (-1 * (calculationPoint.X % CellSize) - CellSize) + cellRect.Y; //reset variables so we dont jump in here next frame _leftSlope = false; _rightSlope = false; //now change the players Y according to the difference of our calculation wantedPosition.Y += newY - calculationPoint.Y; } Video of what it looks like: http://youtu.be/EKOWgD2muoc