Growth

The feeling of gradual empowerment is very feelgood. Ever played Diablo? This is often called "progress", but that's easy to misunderstand. I call it specifically growth. How do you mechanically create growth in a game?

Ramps

A ramp is where the game builds up in some way, as it progresses.

In some games, the activity is complex and interesting enough to be repeated. That's fine. However, most games should ramp up.

If a game doesn't have a ramp, it should probably be a short game. Many of my games are rampless — they just get straight to the action, stay there for a short while, and then end. However, I'd generally recommend having a ramp. It's a tried-and-tested approach, and is much easier to execute than a non-ramping game.

Scrabble doesn't have a ramp. In Scrabble, players just repeat the same activity, until the game ends.
In Magic, players play a land card on each of their turns. As the players have more and more lands, they can play bigger and bigger spells.

A ramp progresses the game to its end. More importantly, it keeps the game changing, and it keeps outdoing itself, with bigger and cooler stuff.

It might be tempting to think "this is just going to snowball, and one player will get out of control." Yes, but that's the fun — seeing whose game can snowball the fastest.

A proper game should have multiple ramps. If there's only one ramp, it's obvious who's going to win, and it's too simple. Give each resource or system its own ramp.

Ramp trajectory

The bigger the ramp, the better (within reason). Your game should begin with the smallest possible actions, and eventually reach actions that almost break the game. Then, it should end.

Avoid having your ramp be reversible. It's okay that some things are reversible (such as resources, money, health etc.), but at least one important thing should just go constantly upward.

The game may ramp up as a whole, but each player should also feel like they're getting stronger.

In my gangster game, you'd get money, and spend it to go to cool locations. Then, you'd have no money, and you were back where you started. It was feelbad. Later, I added information. This was the same as money, but you didn't lose it. So, you could just keep going to more and more expensive locations. That was growth, and it was much more enjoyable.

Players should not just gain rewards. They should also gain permanent benefits like income, discounts, or unlocks.

These benefits will help them for the rest of the game. (The permanent benefit might be an ongoing stream of rewards. That's also fine.)

Cyclical resources

It's quite normal to have cyclical resources or money. However, they should be spent on something that provides permanent benefit.

In Splendor, players take three gem tokens per turn, or they spend gem tokens, to buy cards. These cards provide points, but they also provide a discount on all future purchases. The gems are a cyclical resource — they constantly leave the player, while the bought cards are growth.
In 7 Wonders, each card taken is either a resource or prerequisite, that stays for the rest of the game, and pays for future things.

Costs are cyclical and feelbad. Requirements are growth, and feelgood. (A requirement just demands that you have something, not that you pay it.)

Use more requirements, and less costs.

Cyclical play is a huge trap that adversarial games fall into, as attacking the enemy is typically cyclical, not growth. You attack, and then you're not any stronger.

In my farm game, planting apple trees felt good. You'd plant them once, and they gave you food for the rest of the game. Pine trees, conversely, were planted once, and then you'd later cut them down for wood. That felt bad, as nothing long-term was gained. I changed the pine trees, so that you cut them back to a stump, but the stump kept growing. So that you didn't just remove the wood as soon is it grew, I made trees generate points when they got to a certain height.

As I'm growing tired of crap euro games, I'm increasingly looking at the game being played, or at the back of the box. If each player doesn't have their own board or tableau, the game is probably cyclical and terrible, and I don't want to play it.

Growth is fun. Victory is not. Victory should just be the natural result of growth.

Component accumulation

Having scores that grow during the game is a kind of growth, but you can also just look at a game's components.

Ignore the rules and scores for a second. Where are the physical components going?

If you have a hand of cards, where are they going? What about resources, and other objects? Are they being discarded, or are they amassing in front of you?

If your components aren't amassing, they probably should be.