a simple and clean designed 2d game engine (REFACTORING NOW)

1. a simple and clean API to use, no noise
2. excellent performance
3. easy to extend

glfw, GL, GLEW, glm and a c++11 compatible compiler

1. simple base class for resource manager
2. existing texture manager that can automatically load and unload texture resource based on ref-count
3. only sync loading exists, lack of async loading.

Node based render tree has three core components:

1. Node : base tree node, has basic infomation about the node
2. StageLayer: a Stage which has its own camera and resolution policy
3. Scene : a scene manager which manages one or more StageLayer, input event, scheduler, etc.

ActionManager and Scheduler are owned by a Scene, not globally.

all input handler is registered by attaching a specific event listener to an existing node

1. Pen and Brush to help primitive drawing
2. Abstract File API
3. Enhance event handler
4. Review code and fix bugs
5. more...