ALICE project 4 review

Objective:
	Describe the concept of an event in computer programming
	List and briefly describe the NINE event types used in Alice
	Add an invisible object to mark a spot in an Alice world
	Create new Boolean and numeric properties for an object
	Create an event to move an object
	Create events to allow a user to control a moving object
	Create a billboard object and position it in an Alice world
	Create an event to make a billboard disappear

User Interface and Event-Driven Programming
	Graphical User Interface (GUI) is a combination of computer software and hardware that allows user to operate a computer by manipulating icons and menus on a computer screen, mostly commonly with a mouse that controls a pointer.
	Before GUI were developed, most common interface was Command-driven user interface, in which user operated a computer using commands.


	The use of a GUI on a computer requires Event-Driven-Programming.
	Event occurs whenever an event listener detects an event trigger and responds by running a method called event handler.

	Event Listener -> Event Trigger -> Event Handler

	Event Listener - a combination of software and hardware that continuously checks the computer system for an event trigger.
	Event Trigger - can be any activity or condition selected by the programmer, such as clicking on a mouse or pressing a key on the keyboard, it could also be a change that occurs in a computer itself, ex. when a countdown clock hits 0
	Event Handler - a method that is activated when the event trigger occurs. Ex. pressing "Ctrl + P" on keyboard will display Print page

	Events are used in Alice to control objects while a world is playing. Some Alice worlds are:
		Narrative World, tells a story
		Interactive World, Using keyboard and mouse controls while the world is playing
		Mix of both, like a video game

Examining Events in an Existing Alice World
	BDE event type: when an event is triggered, the event handler has a beginning, during, and end

Nine event types in ALICE: (self explanatory)
	1. When the world starts
	2. When a key is typed
	3. When mouse is clicked on something
	4. When something is true
	5. When a variable changes
	6. Let mouse move ____
	7. Let arrow keys move ____
	8. Let mouse move Camera
	9. Let arrow keys move Camera