Because of how they're packaged, there is no left and right twix. Left and right are relative terms. My left could be your right and someone else's up or down. Before you open a package of twix each twix bar is in a superposition of left and right. They only gain cardinality when you tear open the packaging. Both sides of the packaging are designed to easily open so there is no objective top or bottom to the packaging.
Anon is crazy because he thinks that he can guess which twix is which as if being a left or right twix were an objective term. Sort of like if someone handed you two completely identical copies of a photograph and a marker and told you to highlight the differences, and then you found some differences.
I disagree. The lettering tells you where the top of the package is. There is a top twox and abottom twix, and If you disagree you're being needlessly pedantic and philosophical.
Yeah there's a top and bottom one but there's no left and right one until you've opened it. The only packaging that I can see that indicates which side is the top are the ones which advertise themselves as being all left or all right twix. Regular twix wrappers don't even have "tear here" printed on them.
Depending on where you live Twix packaging has an end like this, which gives you a top of the package to orient yourself to. But that's besides the point because the ad expects you to not think about it too hard and just accept a left and right twix.
Hold it in your hand out in front of you with that top side of the wrapper in view, the left Twix is the one that has a bite taken from it.
Open that end and place it (still containing the two Twix bars on the table) pick it up again and hold it so the top side is facing up and slide out the Twix on the left to eat. It's the one that is on the side that is whole.