Keep your eye on the upper left corner of the screen. (NBC)

Figure skating is a most curious and deceptive Olympics sport, where the exceedingly difficult appears simple and a lack of skill can be shrouded by sequins and sparkle.

And now these Olympics have brought yet another puzzle piece: What the heck are those tiny colored boxes? They pop up in the upper left corner of the screen after every move. Sometimes, the boxes are red. Sometimes they’re green. Sometimes, they are yellow and later turn red. Sometimes, they are yellow and later turn green. They’re traffic lights on ice, accompanied by ever-changing numbers that look like a math problem from “A Beautiful Mind.”

So what’s going on? Those green boxes started showing up on NBC television broadcasts in 2016. Judges do not see them. They are television tools to help viewers have a better sense of how the event is being scored.

If there are a lot of green boxes, that’s an indication that a skater is doing well. If the boxes are red, the skater is probably messing up in subtle but important ways. If they are yellow — well, that’s confusing, because they won’t be yellow for very long.

First, some necessary background: After a judging scandal in the 2002 Olympics, figure skating moved to a complex system that gives points for practically every jump, spin, turn and pose on the ice. Different moves are worth different point totals, depending on their difficulty. Judges then add or subtract points based on how well those moves are executed.

Let’s take the triple axel, for example, since it’s the talk of the Games after Mirai Nagasu made American history by performing it in the team event final. A successful triple axel has a base value of 8.5 points.

How can you tell if a jump or spin is successful? That’s when you look at the box. It is the evaluation made by the competition’s traffic cops, a “technical panel” whose three members are meticulously making sure skaters are utilizing proper entrances and not cheating on their elements.

The first thing the panel pays attention to is the entry into the jump. How a skater launches into the jump makes one triple jump harder than another triple jump, and one quadruple jump harder than another quadruple jump.

For example, the triple axel jump requires the skater to launch forward in the air using one foot with no assistance from the skate’s toe pick, before landing backward on the other foot. Although it is called a “triple axel,” it requires 3 1/2 turns in the air to account for jumping forward and then landing backward. If the skater jumps in another direction or uses the toe pick to vault off, it cannot be evaluated as an axel.

The panel also evaluates how many times the skater rotates in the air, as opposed to on the ice. A skater does not get full credit for a jump rotation if more than ¼ of the rotation is done while a skate is on the ice.

When Nagasu jumped using the proper entrance and completed her 3 1/2 rotations in the air for a triple axel, the technical panel indicated that the jump could be evaluated at its full base value of 8.5 points. And a full base value ruling means the box turns green.

But let’s say that Nagasu only did a little more than three rotations, as opposed to the needed 3 1/2 rotations. The panel would deem the jump under-rotated, and the maneuver would be evaluated from a lower base value. No full base value? That’s when the box turns red.

When the panel makes its call, a separate group of nine judges evaluates how well the jump was executed. Those judges want the jumps to be high, straight in the air, covering great distance on the ice and landed smoothly on one leg. Those criteria are used to deduct as many as three points (if the jump is leaning in the air and the skater has a bad fall, for example) or to add as many as three points (if the jump is perfect). The average score is then added to the skater’s total.

Nagasu was about halfway to perfection for her triple axel: the second group of judges eventually added 1.57 points to her base value of 8.5. That means the element was worth 10.07 points in all, a number that was added to the skater’s technical score.

Those evaluations are usually done almost instantly, and viewers can see the numbers changing as judges punch in their evaluations after an element is completed. But sometimes, the evaluation takes a little more time: if the jump is sloppy, or not very high, or has a funny take off. That’s when the box turns yellow.

It doesn’t stay yellow forever; an evaluation must be made, often using instant replay. When the technical panel reaches a decision, the box will then turn either red or green, this time for good.

Again, this is all to help viewers figure out whether a skater is doing well. The boxes are helpful tools to check on individual moves — mostly, whether a jump has been completely rotated — but they don’t tell the entire tale.

For example: Let’s imagine Nagasu had actually received a red box in the team event, because she under-rotated that triple axel. The move would be evaluated from a reduced base value of 5.9 points, not the full 8.5.

Compare that to Italy’s Carolina Kostner, the beautiful skater who received a green box for her double axel. A fully-completed double axel with a green box is considerably easier than a slightly-botched triple axel with a red box, so the double would have a lower base value of 3.3 points and Nagasu would still receive a higher score on her axel element.

The event’s winner has the highest cumulative score, based on technical points accrued during the routine and a judgment of the skater’s program and presentation that’s received when the performance concludes.

If you’re trying to figure out who is going to win — and not just simply evaluate an individual element — it’s probably better to watch how the technical number displayed on the screen compares with that of the leader. That number provides a better sense of how far behind a skater is when her music stops, before the dramatic reveal of her total score.

Read more:

For pairs figure skating gold, it’s Germany vs. China … and then a battle for bronze

No, Mirai Nagasu does not have a giant ‘USA’ tattoo on her inner thigh

‘The whole thing could just pop off’: South Korean figure skater battles wardrobe malfunction