What is Crystal2Day?

Crystal2Day is designed as a tool to develop games with Crystal fast.

Less work for you, therefore more time for actual game design.

Why should I use Crystal2Day?

Did you ever want to start a game, but then got frustrated while programming something mundane like a scrolling map, finally implemented it and then gave up when you saw the terrifying news of "20 FPS"?

Then Crystal2Day might just be the solution for you.

Crystal2Day is more than just a Crystal wrapper around a media library.

It provides basic game functions, but also some typical game design structures like maps, scenes and entities.

Mostly, it serves as a layer above lower-level game libraries like SDL, without having to worry about common implementation details.

For example, a map class is already implemented, as well as typical collision routines, a framerate limiter, z-ordering, cameras and many other things.

Essentially, you can build a game using a number of scenes, which can be considered as corkboards. Just pin everything you want on there and let Crystal2Day do the rest.

And even if you want to do everything by yourself, you can just do exactly that, as most SDL functions are available in this library.

Currently this project is in an early state, but will be expanded over time. Note that its syntax may change (frequently) until version 1.0.0.

Features

Main features

Based on SDL
Simple framework to immediately start working
Scene system to organize and streamline game design
Already implemented: Cameras, z-ordering, parallax scrolling, maps, collisions, ...
Data-driven entitiy system

Optional features

Behavior scripting using mruby via Anyolite
Simple GUI construction (e.g. for debugging) using Dear ImGui

Prerequisites

Essential

Crystal (obviously)
SDL 2 (media library; SDL 3 is not yet supported)

Optional

Git (for installing additional features)
GCC or Microsoft Visual Studio (for installing additional features)
Ruby (for installing additional features)
Rake (for installing additional features)

Installing

Currently, this shard can simply be used by adding it into your shard.yml, as long as all dependencies are installed correctly.

Make sure to have SDL 2 and its libraries installed, or linking will fail.

If you want to add features like Anyolite or ImGui, you can install them using rake add_feature_XXX, where XXX is one of the following features:

anyolite - Support for scripting using mruby
imgui - A simple GUI application, useful for debugging

It is also possible to install these manually. Crystal2Day will automatically include these features, if they are found in the lib directory (for example after installing them as shards together with Crystal2Day).

NOTE: For ImGui to work on Windows you need to copy both cimgui.dll and cimgui.lib from the Crystal2Day directory to your working directory or set the Crystal environmental variables so that they are included.

A simple example

To get started, here is a simple example, which will simply open an empty window:

require "Crystal2Day.cr"

# Just create a customized Scene class
class MyOwnScene < Crystal2Day::Scene
  # Any events are passed to this method
  def handle_event(event)
    if event.type == Crystal2Day::Event::WINDOW
      if event.as_window_event.event == Crystal2Day::WindowEvent::CLOSE
        # Signal the program to stop the main loop
        Crystal2Day.next_scene = nil
      end
    end
  end
end

# All setup for the framework is done in this block
Crystal2Day.run do
  # If we only have one window, the framework stores a reference to it
  Crystal2Day::Window.new(title: "Hello World", w: 800, h: 600)
  # Set the next scene
  Crystal2Day.scene = MyOwnScene.new
  # Start the game
  Crystal2Day.main_routine
end

Roadmap

Version releases

Version 0.1.0

Features

Music and sounds
Textures, sprites, fonts, texts
Basic shapes (points, lines, boxes, circles, triangles, ellipses)
Z-Ordering
Scene system
Support for multiple windows
Framerate limiter
Maps and tilesets
Basic support for maps created with the Tiled editor
2D collision routines
Entity hook system
Optional scripting using Anyolite
Entities with flexible states and multiple script pages
Entity collision system
Simple game state
Resource management system
Special plugin system
Imgui support

Urgent todo list

Currently none

Open design questions:

How should the examples be structured?
What is the best way to install additional features?
Should all shards be installed, but their postinstall hooks only be triggered when desired?
What examples should be made?
Could entities be bound to maps?
How should tilesets with overlapping segments be implemented?
Is the current map streaming way really okay?