New patterns are often discovered by doing things backwards, the most obvious example is the Cascade & Reverse Cascade. Things get more interesting as you try to attempt to reverse more complex patterns. Mills Mess is strange because the pattern is almost (but not quite) exactly the same as it is forwards. This is not a trick which audiences will go wild for, most jugglers can't tell the difference between Mills Mess forwards & backwards. So why am I writing this tutorial? Purely academic reasons.
You can skip the next two paragraphs if you like they aren't really necessary to learn the pattern.
First of all think about the three types of throw that make up Mills Mess & think what would happen to each throw if you were to watch the pattern on a video playing backwards.
One is the back toss, which is the throw made on the opposite side of the pattern to return to the same side. It is thrown by the top hand when the arms are crossed & is caught by the upper hand when the arms are crossed the other way. This throw is absolutely symmetrical so when the move is performed backwards it looks exactly the same as it does forwards. In Inverse Mess this throw doesn't change at all. Another throw is the over the top throw, which is the only throw made when the arms are uncrossed. The ball is thrown so that it follows the path of the back toss & it is caught by the lower arm when the arms are crossed as an Under the arm catch. The reverse of this throw is an under arm throw caught by the opposite hand with the arms uncrossed. Lastly the ball thrown Under the arm travels in a 'U' shape. It is caught on one side of the pattern then carried to the opposite side then thrown straight up. Play it back & the ball is caught under the arm carried back to the same side then thrown straight up.
Strangely, to create this pattern all you have to do is alter one throw of the standard Mills Mess. So start juggling Mills Mess & watch what happens as you start to swing your arm for an Under the arm throw. When crossing your arms over freeze the pattern at the point where your arms are level, one above the other & take a look at the position you are in. Those that lack telekinetic abilities will have to use their imagination for this bit.
Both hands are holding a ball & the third ball is stuck in mid air. The arm on top is in the process of moving away from the floating ball & the hand on the bottom is moving towards it. When juggling a standard Mills Mess you carry on moving the lower arm all the way to the other side & throw the ball up on the opposite side of the pattern, on the outside of the floating ball.
To juggle Mills Mess backwards you need only carry the ball with the lower hand to the centre of the pattern & then throw the ball in between the ball in the air & your other arm. Catch the other ball under the arm, carry it back to the same side as you uncross your arms & throw it straight up. Then make the next under arm throw between this ball & your other arm.
That's all there is to it. It is a nice easy one to learn, just juggle Mills Mess & pop in the occasional 'in between' throw in place of the under arm throw & work up to doing it on each side every time.