# Creating a trick

Most tricks are fairly straight-forward to implement. You create a class which extends `Trick` and override the `activate` method. 
Here is a simple example:
```java
public class IsEvenTrick extends Trick {
    public IsEvenTrick() {
        super(Pattern.of(3, 4, 5));
    }

    @Override
    public Fragment activate(SpellContext ctx, List<Fragment> fragments) throws BlunderException {
        return BooleanFragment.of(expectInput(fragments, FragmentType.NUMBER, 0).number() % 2 == 0);
    }
}
```
Let's break this down. We've made a new class, `IsEvenTrick`, which extends `Trick`. 
We've overridden `activate` and passed a `Pattern` to the super constructor. 
The `Pattern` we passed is the pattern in-game that maps to this trick. 
Using a pattern already used by another trick results in the last one registered replacing all others, so be careful which pattern you pick. 
The `activate` method is where the logic of `IsEvenTrick` lies. 
When this trick is executed, it receives the context of the current execution and the fragments that resulted from evaluating all the child circles. 
`IsEvenTrick` calls `expectInput`, a function available to all inheritors of `Trick`, which takes a list of fragments, (optionally) a `FragmentType`, and an index. 
It will return the fragment of the appropriate type at the index given, or throw a [`BlunderException`](Making-Blunders.md) if there is none, or if it encounters a type mismatch. 
The returned fragment is a `NumberFragment` in this case. 
`IsEvenTrick` returns a new `BooleanFragment` whose value is equivalent to the result of `n % 2 == 0`.

# Registering a trick

So you've got a trick implemented. But you need to register your trick before it will be available in game. 
To do this, we simply call `Registry.register(Tricks.REGISTRY, Identifier.of("mymod", "is_even"), new IsEvenTrick());` in the addon's main initializer. 
Be sure to replace `mymod` with your addon's ID!

Your new trick should now be available in-game, but there's something missing still...

# Translations and documentation

If you tried to use `IsEvenTrick` in-game without passing it a number, 
you may have noticed that the blunder in chat doesn't display the trick's name, but rather its translation key. 
You can add the translation for that key in your language file as you would any other translation. 

Now, the final step: adding an entry to the Tome of Tomfoolery. 
While this isn't necessary, it is highly recommended, as otherwise there will be no way for players to know how to draw your trick without looking at the code themselves. 

In your mod's assets (`resources/assets/mymod`), create the file `lavender/books/tome_of_tomfoolery.json`. In it, add the following snippet:
```json
{
  "extend": "trickster:tome_of_tomfoolery"
}
```
Then, create the directory `lavender/entries/tome_of_tomfoolery`. Within this directory, create a markdown file. 
You may name it anything, as long as it contains only underscores and lower-case letters. At the top of this file, include a JSON code block, like so:
````markdown
```json
{
  "title": "Addon Trick",
  "icon": "minecraft:stone",
  "category": "trickster:tricks"
}
```
````
Make sure the title, icon, and book category are correct! 
For more info on the available properties an entry can have, please refer to the [docs](https://docs.wispforest.io/lavender/metadata-format/). 
Then, beneath this code block, you can put a short description of this entry. 
```markdown
Cool tricks to impress your friends!

;;;;;
```
The five semicolons at the end denote a page break. For more info on Lavender syntax, please refer to its [documentation](https://docs.wispforest.io/lavender/markdown-syntax/). 
Following this page break, we can add our first entry:
```markdown
<|glyph@trickster:templates|trick-id=mymod:is_even,title=Even Distortion|>

number -> boolean

---

Returns whether the given number is even.
```
Be sure to replace `mymod:is_even` with the correct identifier, and to change the string after `title=` so it matches the translation. 
And finally, you have your first trick available in game, with an entry in the Tome of Tomfoolery, so it can be found!

# Ploys

//TODO: `tryWard`, `useMana`, `expectCanBuild`, and mana usage Lavender element