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Your first Buzz script

Eggy's dev console runs Buzz, a small, statically typed scripting language. In this tutorial you will try Buzz a line at a time, then write a script file that adds a slowmo function to your game, run it, fix a mistake in it, and run it again.

Before you begin​

You need an Eggy project that opens in the editor. Buzz runs on desktop (Windows, macOS and Linux); the web and Android builds run console commands only.

1. Open the console​

Press Play, click into the game so it has the keyboard, then press </kbd>. A bar opens along the bottom of the game with the prompt **Write your command**. Press <kbd> again, or Esc, to close it.

The editor's Console panel has the same prompt under its messages, and both share one session: what you declare in one, you can use in the other.

2. Try a few lines​

Type each line and press Enter:

print("hello")
hello

A line that ends in a value shows it:

1 + 2
3

What a line declares stays for the lines after it:

var speed = 3;
speed * 2
6

Type help to list the console's commands. A line whose first word is a command runs that command; anything else runs as Buzz. Press Tab to complete commands, entity names and the names you have declared, and Up to bring back an earlier line.

3. Write a script file​

Typing works for one-off lines. For anything longer, write a file. In your project's folder (the one with build.zig), make a folder named scripts and save this as scripts/slowmo.buzz:

// Slow the game down, or speed it back up.
fun slowmo(scale: double) > void {
    if (run("timescale {scale}")) {
        print("Time now runs at {scale}x");
    } else {
        print("Couldn't change the time scale");
    }
}

print("slowmo is ready: try slowmo(0.25)");

A few things to notice:

  • fun declares a function. Each parameter has a type, and > void says it returns nothing.
  • {scale} inside a string puts the value of scale there.
  • run runs a console command, here timescale, and returns whether it ran.

4. Run it​

In the console, type run scripts/ and press Tab: it completes to scripts/slowmo.buzz. Press Enter:

slowmo is ready: try slowmo(0.25)

The script ran from top to bottom, and slowmo now exists for later lines. Call it:

slowmo(0.25)
Time now runs at 0.25x

The game slows to a quarter of its speed. Put it back:

slowmo(1)
Bad argument type: got type `int`, expected `double` (column 8)

Buzz never turns one type into another for you. 1 is an int and slowmo takes a double, so write 1.0:

slowmo(1.0)
Time now runs at 1x

5. Change the script and run it again​

Let slowmo take whole numbers too, by adding a second function to the file:

// Slow the game down, or speed it back up.
fun slowmo(scale: double) > void {
    if (run("timescale {scale}")) {
        print("Time now runs at {scale}x");
    } else {
        print("Couldn't change the time scale");
    }
}

// Back to normal speed.
fun normal() > void {
    slowmo(1.0);
}

print("slowmo is ready: try slowmo(0.25), then normal()");

Save it and run it again with run scripts/slowmo.buzz (or Up to find the line). Running a script again replaces everything it declared last time, so you can keep editing and rerunning it while the game plays. Now normal() works.

6. Read an error​

Make a mistake on purpose. Change the last line to:

print(42);

and run the script again:

Bad argument type: got type `int`, expected `str` (scripts/slowmo.buzz:15:8)

An error names the file, the line and the column. A script that fails changes nothing: the slowmo and normal from the last run that worked are still there. Put the line back the way it was, or write print("{42}"), and run it again.

What's next​