Billy

The goal of the project is to create a very small, easy-to-understand set of features which can combine to create complex and fun interactions.

This project was inspired by Isla, a project by Mary Rose Cook.

Please fork to help out, or submit an issue if you find a bug.

Billy is released under the MIT License. See LICENSE.md for details.

Try it out.

The Language

Characters are represented by geometric shapes, and have attributes.

To make a new character:

[name] is a [type]

where [name] can be any string matching [A-Za-z]+, and [type] is one of: circle, ellipse, oval, square, rectangle, or triangle.

Each character has several attributes, which define its appearance.

Each character has attributes x, y, left, right, top, bottom, red, green, blue, radius, size, height, and width.

An expression alters a character's attribute. There are two kinds of expressions: 'set' expressions, and 'move' expressions.

'Set' expressions set a characters attribute to a value, and are of the form:

[name]'s [attribute] is [value]

'Move' expressions move a characters attribute by an offset, and are of the form:

move [name]'s [attribute] [offset]

The "'s" can be omitted.

Conditionals allow a user to define interactivity. A user can bind an arbitrary keyboard key to an expression.

when i press [key] [expression]

Once this conditional is created, whenever [key] is pressed, [expression] will be evaluated.

A variable is a key which is bound to a number. It can be substituted anywhere a number literal is used.

[key] is [value]

delete [character]
remove [character]

removes a character from the environment

reset

resets the environment, removing all characters, key bindings, and variables

up

minimizes the command prompt

down

maximizes the command prompt

save

saves a screenshot of the canvas