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Creating Point and Click Games with Escoria

Booleans and Conditions

Conditions are the way to take decisions based on the current state of your game. They are built around boolean values. A boolean value is a value that is either true or false.

To make use of these, you have to know about the set_global command we explained in the previous "Global states and saving" chapter

This command sets a global flag to a certain boolean value. For example:

set_global player_has_money true

To sum this up, we can say we will use set_global to remember the player has done something we might need later. Now that you understand this, conditions are a natural consequence of the presence of boolean values in Escoria. Because if we need later to know if the user made a previous action to give him the possibility to do another, we’ll need to write a condition.

Conditions enable you to take different actions based on some global flags. Briefly we will be able to check the value of a global and give the user the right gaming options, corresponding to what has been stored in globals.

To execute an esc command conditionnaly, all you need to do is to add a list of global flags at the end of your command, like so: [flag1, flag2, flag3]. The command will run if all the flags of the list have a true value.

You can also negate a flag in the list by preceding it with a ! character, this will execute the command if the flag is false.

In this exemple, the first line happens only if the player_has_money is false or unset. The second line happens if the global has been set AND if parents_are_there is false (the comma means that both has to be ok).

say shopkeeper "Go away you little brat!" [!player_has_money]
say shopkeeper "Hehehe, there you go, here’s your candy bar." [player_has_money, !parents_are_there]

Of course, the game may have many conditions depending of the complexity of the scenes and the problems to solve. And often, several things will happen if a global is set correctly to our wishes. In this case, we’ll need a block as defined in the previous Structure chapter.

One of the most useful features of conditions is that you can use them with blocks, effectively running the entire block based on the conditions list like so:

> [introduced, picked_item, !god_appeared]
say old_man "Good! Now offer it to our almighty panda god, I’ll summon them for you."
set_global god_appeared true
set_active bamboo_god true

These three commands (say, set_global, set_active) taken from our sample game will only run when introduced and picked_item are true, and god_appeared is false. There are many other example of conditions in this little game. For example, the player can take the bamboos only if he has already spoken to the old man. Here, on talk verb, we open a block that will happen if the introduced global is not set. This is the global we will use to remember if the player did talk to the old man. In this case, the old man talks and sets the introduced globals to true, to that we can do another action (pick the bamboo) later or if we come back to the old man so that he can say something else.

In the old_man.esc we have

:talk

> [!introduced]
    say old_man "Hello young panda, today is time for your first offering to the almighty panda god! I have prepared a bamboo stick for you, pick it up and bring it to me." default avatar_old_man
    set_global introduced true
    stop

Then the block if he already introduced

> [introduced, picked_item, !god_appeared]
    say old_man "Good! Now offer it to our almighty panda god, I’ll summon them for you." default avatar_old_man
    set_global god_appeared true
    set_active bamboo_god true
    stop

Where we make the god appear. We have mixed the introduced state with other global, because we want to answer this if the player has picked a bamboo too.

Finally, we use it in the bamboo esc files too to enable the picking of the bamboos only if the players as talked to the old man and if no bamboo has been picked up. This example is taken from good_bamboo.esc :

:pick_up

> [introduced, !picked_item]
    set_global picked_item true
    set_global i/inv_good_bamboo true
    set_active good_bamboo false

If the action matches no conditions, a fallback action can be provided.

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