The second part of this analysis will cover three types of in-game items: Restoring (Medikits, Salts Bottles, Food/Beverage), Lockpicks and Silver Wings. Gears, Weapons and Vigors will be covered in a separate publication as they are a big enough topic on their own.

Anyway, let's get started!

Items

Items are a core element in Bioshock Infinite, as they allow to recover HP, mana, ammos, as well as buying other items or upgrades.

Restoring

Restoring items are: Medikits (HP), Salts Bottles (Salts), Food/Beverage (lower HP and Salts).

Keep in mind that food/beverage not only restore less, but might also drain HP or Salts and alter the player's vision(1), so their value on the graphs isn't as valuable as medikits' or salts bottles'. 

Figure 2

First the food's curve: from around 0 to almost 100 in the second level, above 100 in the next one, back close to 0, another spike, a steep decrease and then almost the same pattern but mirrored.

Let's break this down:

In the very beginning, the character doesn't start with full HP, so food is spread around the area to make the player look for it (to heal), therefore leading him to explore, and making him interact with the world, beginning his immersive process into the game.

It's all player's agency.

Another step into this process is presented since this part: "Heal yourself" isn't a task told by the game, it's the player himself who (seeing a half-empty HP bar) feels the need/desire to heal and, instead of running from one point to the next one, feels free to search around for food.

Conclusion number three: A task internally developed by the player can lead to an immersive experience from the very beginning, if felt as his own and part of his freedom in the game world.

Food is also used to provide smaller sustain while keeping the player inside the loop: Look for supply, interact with the world, fight enemies (which will consume player's HP/Salts), and back to looting.

Enough about food, what about Medikits and Salts Bottles?

Analyzing their curves, even though they have a similar trend (with a few exceptions), it is clear how Salts Bottles are more present in the playthrough than Medikits, and the reason in mainly one. The developers want the player to use his Vigors, to stress the fact that it is not a "spray and pray" game: weapons are not the only choice to fight enemies.

This probably couldn't be more stressed, since the game itself shows messages about using Vigors if you haven't in the previous minutes, especially in the beginning of the game. This is evident in Finkton Proper: medium food, below-average Medikits and a Salts Botles spike.

Conclusion number four:  You can't predict the dynamics of the game, but you can push a player's behavior on your track in direct ("Remember to use vigors" pop-ups) or indirect (provide different resources to make him adjust his playstyle) ways.

Lockpicks

Figure 3

This is a rather short topic: Lockpicks are initially(2) provided in a slightly higher number than needed, in case the player doesn't find them all (the game is not punitive from this point of view). This is also a Bottom dollar effect, not making a player use all his lockpicks allowing him to have some extras.

However, there are areas where the needed amount is higher than the lockpicks present in the area, to punish players who look for them only when they see a lock, making them explore more in future.

In Downtown Emporia the player is highly rewarded for exploring, and the high amount of lockpicks there increase the chance of the player being able to access locked rooms/safes in the last areas.

Silver Wings

Silver Wings are the main currency of the game, used to buy items, upgrades and to be revived(3).

Figure 4

As for the food, the early areas are mainly to introduce the player to the world and it's exploration; Further on, though, the curve gains a trend of spikes and decreases, but never reaches the zero (except for the ending, as there is no way of spending money and the focus is on the narrative).

This provides two ways of how the money is spent:

Also, never finding zero money keeps the player in a sense of:

Conclusion number five: Using both short (collecting coins) and long (buying a desired upgrade/item) term rewards helps keeping the player in the flow(4), and giving him a sense of constant progression, secret of a long and immersive gameplay.

The amount of available Silver Wings, however, isn't enough to purchase all available items, and this leads to this week's last conclusion.

Conclusion number six: Having one currency for multiple uses, and being this currency limited, increases the currency's perceived value by the player, engaging him in a loop: "Money has multiple uses so i need it -> I need to find it -> i need to explore -> I find money -> I spend it -> I need it again for something else"

The player gets rewarded with money, giving 1 Silver Wing the value of "1 Silver Wing + the effort spent to find it".

This concludes this week's topic.

TL;DR: Making the player creates his own goals increases his immersion; We can't predict dynamics but we can adjust (directly and indirectly) the player's behavior; A combination of short-term and long-term goal helps keeping the player engaged; A limited currency has higher perceived value than the currency itself as in include the player's effort to obtain it.

These were some of my favourites conclusion, as they help to break down how Bioshock Infinite engage the player on multiple levels in a way no other game I have experienced does.

Are these fundamentals rules enough to build the core of an engaging experience? What could have been done better in your opinion? I'd love to read your thoughts about it!

Thank you for taking the time to read this, I really appreciate it. Feedbacks are always welcome.

If you missed it, the first part of this analysis can be found here, covering Introduction and Duration.

Next week's topics: Gears, Weapons, Vigors. See you there!

Notes:

1) Drinking multiple alcoholic bottles leads to "drunk" state: blurred vision and camera shakes.

2)Since the first lockpick can be found; In the previous areas there are none because of the absence of Elizabeth or her recent arrival, avoiding her player's perception as mere tool to pick locks and find resources.

3)In 1999 Mode, upon the player's death 100 Silver Eagles will be paid to respawn him

4)Flow as "sense of progression via rewards"