All of these have one thing in common - that you pay for them with real-world money, without knowing what’s inside.

Loot boxes have become so controversial that some types have been banned in a few countries. It’s because they can make players act in a certain way, which might not be good for them.

These are five main tricks the game designers use to do this:

1. Juiciness

Loot boxes are built to seem exciting - they are bright, flashy, dramatic, and have sounds and visual effects that grab your attention.

In game design, we call this "juiciness", and it really works to entice players to keep buying loot boxes, keep opening them, and keep getting the "excitement" that comes with them.

2. Skins

In video games we all want our characters to stand out, and instead of earning new costumes through gameplay, loot boxes allow you to simply pay for them.

However, which skins you get is unpredictable, and so you're encouraged to keep buying loot boxes to try and get the appearance you really want.

3. The will to win

Other rewards can directly affect your gameplay experience, by making your character stronger, tougher or faster. This allows you to progress through a game more rapidly than your friends.

So why work for that, when you can just pay for it? The desire to win in the game can pull you into paying for more and more loot boxes, and your friends do the same to keep up, all getting caught in a "race" to buy the best items.

4. "Free" loot

Games often claim you’re getting “free” loot boxes, if you spend more money. So the more you pay in total, the less you pay per loot box.

This encourages you, the player, to spend more money at once in order to get those "free" loot boxes, and to spend more money as a whole.

5. Loot envy

Because other players can see what you get from loot boxes, they are also designed to both help you show off your items - encouraging your friends to buy loot boxes - and to help your friends show off, making you want to buy loot boxes!

In both cases the games are designed to make friends feel jealous of what others have, and purchase loot boxes to compete.

Knowledge is power

These are the ways loot boxes are designed to make you invest more of your time and money into playing. And for some, playing more and more could be the start of something serious.

So it’s good to be aware of these tricks. That way, if you spend money on loot boxes, at least you can understand why you’re doing it.

Keeping these things in mind will help to make sure you can still enjoy all the good bits of gaming.

Dr Mark R Johnson is one of Own It's experts and supporters.