function mainJump():void{
        //When this function is called...
        //If we're not jumping...
        if(!mainJumping){
                //Now we are jumping...
                mainJumping = true;
                //And our jump speed is the maximum jump speed.
                //Since (0, 0) is the top left corner, we have to subtract to go up.
                //As such, we multiply jumpSpeedLimit by -1 (we could have also said "jumpSpeed = -jumpSpeedLimit").
                jumpSpeed = jumpSpeedLimit*-1;
                //However, setting our jump speed alone does not move our character. We now must modify our character's
                //position by the amount in jumpSpeed.
                main_mc.y += jumpSpeed;
        //However, if we're already jumping...
        } else {
                //If our jump speed is less than 0, meaning the character is still going up...
                if(jumpSpeed < 0){
                        //Our jump speed is multiplied by 1 minus the maximum jump speed divided by 75 to slowly degrade
                        //the jump speed by a factor of (1 - jumpSpeedLimit/75), creating the first half of the arc.
                        jumpSpeed *= 1 - jumpSpeedLimit/75;
                        //However, if our jump speed is greater than 1/5 of our maximum jump speed in the upper direction...
                        //Remember that being greater than 1/5 of our maximum jump speed means our jump speed is approaching 0,
                        //meaning that we will have to change our behavior to account for it soon, since we can only go up
                        //if our jump speed is less than 0.
                        if(jumpSpeed > -jumpSpeedLimit/5){
                                //Multiply our jump speed by -1 so that it begins our descent, creating the beginning of
                                //the second half of the arc.
                                jumpSpeed *= -1;
                        }
                }
                //However, if our jumpSpeed is greater than 0, meaning we are falling, and our jump speed is also less than
                //our maximum jump speed (no longer negative, as we are falling, heading away from (0, 0))...
                if(jumpSpeed > 0 && jumpSpeed <= jumpSpeedLimit) {
                        //Multiply our jump speed by a factor of (1 + jumpSpeedLimit/50), pushing us closer to our maximum jump speed.
                        jumpSpeed *= 1 + jumpSpeedLimit/50;
                }
                //Now that we've decided what our jump speed should be this step, we add it to our y position to move our character.
                main_mc.y += jumpSpeed;

                //If the character hits the bottom of the screen minus its height (so that it is still visible)...
                if(main_mc.y >= stage.stageHeight - main_mc.height) {
                        //Our character is no longer jumping.
                        mainJumping = false;
                        //And its y position should stay at the bottom of the screen minus its height.
                        main_mc.y = stage.stageHeight - main_mc.height;
                }
        }
}