The devil, they say, is in the details. This makes grim sense to me, as I'm being tortured by what seems to be my own personal demon, a foul creature which stabs at me from the depths of minutiae that I can not seem to delve into any satisfying extent. Percentages roar angrily around my head, and numbers course relentlessly through my veins. I was not always like this.

I just wanted to play Shadow Of The Tomb Raider.

I had not played a Tomb Raider game for about two decades, but I thought I'd give this a go for a couple of reasons. Firstly, I was curious to see how the series had come over that time. Secondly, it's free with Xbox Games With Gold.

So, I played for a few hours. The graphics were very pretty, Lara sort of looked like a real woman, and the game was fun (if somewhat derivative). I enjoyed myself. Eventually of course, the call of real life could no longer be ignored, so I turned the game off and played the role of a fully functioning human adult. The next day, I returned to the game.

That's when everything started to go wrong.

The title screen now proudly displayed a completion percentage. A very specific percentage. 7.94 per cent to be exact. So, I had seen 7.94 per cent of everything the game had to offer. Or what I maybe 7.94 per cent of the way through the story? Hmm.

I loaded up my save, and dug through the menus to investigate. I found … nothing. Nothing to break down on the title screen, nothing to tell me what the numbers mean at all.

Somewhat disturbed, I quit without playing. I soon discovered that I had developed an unscratchable mental itch. A desire, a needto break down and understand how and why I was playing in the games that I was playing.

The Tomb Raider development team I'm using to interview you with the shadows of The Tomb Raider development team. Although the Square-Enix staff were incredibly friendly and helpful, in the end, looking at interview could not be arranged. I tried to forget about it by playing some other games and, well … that did not quite work out.

GTA 5 was a bad place to start, what with its completion percentages by character. Wolfenstein Youngblood What kind of satisfying – by examining my save file, as well as a detailed breakdown of other tasks and stats in the game – but it did not exactly take my mind off things.

Then I made a truly horrifying discovery, one which self-defense systems in my brain had erased from my memory. The Witcher 3, XP progression bar aside, has no completion meters of any kind. None at all! So much to do, so many hours of content, and no bars or percentages to measure and track what I've done and what I've yet to do.

Thankfully, there are two experts on these matters, miraculously, did not flee in terror at my inquiries regarding such statistics and their use.

Celia Hodent is a UX expert who has worked with companies including Ubisoft, Epic Games, and Lucasarts. UX is a relatively new discipline in the industry. It's a bit tricky concept to explain; it means 'user experience', with the emphasis on 'experience'. A common misconception is to equate UX with UI.

"User Interface is definitely part of UX," Hodent tells me. But UI is just a little part of UX. UX is really everything Players are going to experience, including marketing and community management […] [UX means] not just talking about UI, but talking about sound design, about game design, about level design, about marketing, and community, toxicity, all that. "

Hodent realized that UX was not as widely understood as it is in other areas of business, and there was no book to help teach people about its application to video games – so they wrote one. The Gamer's Brain: How Neuroscience And UX Can Impact Video Game is not cheap is absolutely fascinating. The first half of the book talks about several areas of cognitive psychology, and then the second half explains how and why this is relevant to game development.

But I'm starting to work at Ubisoft in 2008. They always want to. "My background is in cognitive psychology," Hodent explains, "How to do the brain works and learns make their games more enriching for players, [and] I quickly realized that all knowledge about the brain works is useful for any game, because playing a game is a learning experience. You have lots of stuff to learn, the mechanics, the storyline, your goals, etc etc. So you have a lot of things to process, and you have to master the game. So all that happens in your mind, and I soon realized that all this knowledge is not only useful for educational games, or serious games, but for any game. "

Hodent left Ubisoft years ago, but the company has clearly embraced the concept of UX. Scott Phillips, game director of Assassin's Creed Odyssey, explains the process of deciding what to quantify when it comes to progression stats.

"Generally, the question of what to do with a game of progress and the mechanics are in the game," Phillips says. Vertical progression – or mechanics that can make positive choices for players based on what we are looking for on their playstyle – horizontal progression … For players, being able to see progression information allows them to take that better, they are getting better at the game, mastering the mechanics, and growing can also be felt in the experience, which, if balanced properly, makes the player feel more powerful and maintains a enjoyable level of challenge. "

This makes perfect sense, and I start to understand why I crave validation from numbers, bars, and other visible signs of progress. I know I'm moving forward, getting better and stronger; these elements confirm that to me. That confirmation of my progress, I think, is almost a reward in and of itself – evidence that all the hours. Hodent elaborates, framing this sense of progression in, more human terms.

After briefly explaining the concepts of extrinsic motivation and intrinsic motivation, she says, "The main theory of intrinsic motivation is that." is the most reliable so far is called self-determination theory, or SDT for short.

When you see that you are progressing toward something, you feel that you are learning more about it are getting better at it […] it's not just to show that you've reached a certain goal, and you're going to have a specific reward associated with that goal. So you feel better, because you see yourself progressing in doing certain things.

If you do not see yourself progressing every day, at some point you're just going to quit. If you make some effort to lose weight, usually the first few weeks you loose weight every week, so you're happy, motivating you to keep going because you see a progression towards your goal Like, 'Fuck it. It's like this.', 'Fuck it 'why I am going to make the effort when I'm not progressing any more?' re going to quit. "

Phillips unintentionally echoes these sentiments, further proving the value of UX to game design. "If there is any universal rule to the psychology of progression," he says, "I would state it as: start small and end big. In video games, we use progression mechanics that align with existing instinctive mental models that are reinforced in daily life. In terms of quantifying progression, we do that based on the system and the overall needs of the game and the desired player experience very customized to each game and each system.