# Remembering what is happening

[Programming guides](README.md)

A program's **state** is the information that describes what is happening right now. In a game, it might include the score, the remaining lives, and whether a door is open.

State changes when something happens. Picking up a coin changes a total. Pressing a button might change a menu choice. A variable lets a program remember one of these values between instructions.

## Remember a board game

If you pause a board game, you need to remember whose turn it is and where the pieces stand. Those details describe its current state. Without them, you would have to start again.

A computer game has a similar problem. Drawing a door does not by itself remember whether the player is allowed through it. We can keep that information in a Boolean: a value that is either true or false.

## A door and a key

```pliro
# language: en
let hasKey = false
let doorOpen = false
set hasKey = true
if hasKey:
    set doorOpen = true
if doorOpen:
    say "You may enter."
else:
    say "The door is closed."
```

This tiny example represents picking up the key with `set hasKey = true`. It prints the result instead of drawing a game. `hasKey` and `doorOpen` are separate pieces of state: having a key and opening a door are different events.

## Predict, then run

Which message should appear?

```text
You may enter.
```

Now imagine removing the line that gives you the key. The starting value would remain false and the door would stay closed.

## Your challenge

Add a `lives` variable starting at three. Represent one lost life by subtracting one. Display the remaining lives. Keep the door state separate from the number of lives.

## A common mistake

Using `let` inside a repeated block to recreate a score can reset it every round. Create the lasting score before the loop and use `set` to update it. Also remember that ordinary runtime variables are not permanent saved data. A fresh run starts from its initial values unless you deliberately load saved information.

## Where next?

[Following a program](tracing.md) · [Game screens](game-screens.md) · [Saving data](storage.md)