@sara.sa I have gotten past this exercise and feel like I've been bitten very hard for how I implemented my solution later on down the line, so please take what you're about to read with a grain of salt (though what I did here did pass muster per the check-up activity coming up ahead). A couple of hints for your last couple of functions: If your values are moving in the wrong direction, try changing the sign of the value governing how far it moves. One of your arguments may be compared closely to a time displacement vector, and as such it has both magnitude and direction. Also, you may not need all the conditionals you're applying. You might try dropping them in turn to see if you hit paydirt.
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