Assignment 6: “Angry Birds, The Tri-Shot Update”

Objectives

• Read and understand all of the Angry Birds source code from Lecture 6.
• Implement it such that when the player presses the space bar after they’ve launched an Alien (and it hasn’t hit anything yet), split the Alien into three Aliens that all behave just like the base Alien.

Getting Started

Download the distro code for your first game from https://cdn.cs50.net/games/2019/x/assignments/6/assignment6.zip and unzip assignment6.zip, which should yield a directory called assignment6.

Then, in a terminal window (located in /Applications/Utilities on Mac or by typing cmd in the Windows task bar), move to the directory where you extracted assignment6 (recall that the cd command can change your current directory), and run

cd assignment6

Three’s Company

Welcome to your sixth assignment! This week, we took a look at the fundamentals of Box2D, one of the most widely-used 2D physics engines, and how it ties into LÖVE, with its built-in wrappers for it. This assignment will be a little simpler than some of the previous ones (indeed, there’s only one core objective, albeit a reasonably complex one) but will still require knowledge of Box2D and the distro before we can dive in too quickly.

Your goal this assignment:

• Implement it such that when the player presses the space bar after they’ve launched an Alien (and it hasn’t hit anything yet), split the Alien into three Aliens that all behave just like the base Alien. The code for actually launching the Alien exists in AlienLaunchMarker, and we could naively implement most, if not all, of this code in the same class, since the Alien in question we want to split off is a field of this class. However, because we want to only allow splitting before we’ve hit anything, we need a flag that will get triggered whenever this Alien collides with anything else, so we’ll likely want the logic for this in the Level itself here, since that is where we pass in the collision callbacks via World:setCallbacks(). The center Alien doesn’t really need to be modified for the splitting process; really, all we need to do is spawn two new Aliens at the right angle and velocity so that it appears we’ve turned the single Alien into three, one above and one below. For this, you’ll need to take linear velocity into consideration. Additionally, be aware that the Alien we want to launch has the userData of the string “Player”, as opposed to the Alien we want to kill, which has just the userData of “Alien”. Lastly, be sure that the launch marker doesn’t reset until all of the Aliens we fling have slowed to nearly being still, not just the one Alien we normally check. In all, you should have all of the pieces at this point you need in order to make this happen; best of luck!

How to Submit

1. If you haven’t already, install Git and, optionally, install submit50.

2. Using Git, push your work to https://github.com/me50/USERNAME.git, where USERNAME is your GitHub username, on a branch called games50/assignments/2019/x/6 or, if you’ve installed submit50, execute

   submit50 games50/assignments/2019/x/6
   

   instead.

3. Record a 1- to 5-minute screencast in which you demonstrate your app’s functionality and/or walk viewers through your code. Upload that video to YouTube (as unlisted or public, but not private) or somewhere else.
4. Submit this form.