Angry Birds

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.

Demo

by Edward Kang

Getting Started

Download the distro code for your game from cdn.cs50.net/games/2018/x/projects/6/angry.zip and unzip angry.zip, which should yield a directory called angry.

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 angry (recall that the cd command can change your current directory), and run

cd angry

Three’s Company

Welcome to your seventh 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.

Specification

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

When you submit your project, the contents of your games50/projects/2018/x/angry branch must match the file structure of the unzipped distribution code exactly as originally received. That is to say, your files should not be nested inside of any other directories of your own creation or otherwise deviate from the file structure we gave you. Your branch should also not contain any code from any other projects, only this one. Failure to adhere to this file structure will likely result in your submission being rejected.

By way of a simple example, for this project that means that if the grading staff visits https://github.com/me50/USERNAME/blob/games50/projects/2018/x/angry/src/AlienLaunchMarker.lua (where USERNAME is your own GitHub username as provided in the form, below) we should be brought to the AlienLaunchMarker.lua file for Angry 50. If that’s not how your code is organized when you check (e.g., you get a 404 error or don’t see your edits), reorganize your repository as needed to match this paradigm.

If you haven’t done so already, visit this link, log in with your GitHub account, and click Authorize cs50. Then, check the box indicating that you’d like to grant course staff access to your submissions, and click Join course.

The change to /projects/2018 below is intentional, as CS50 courses have changed to a scheme that reflects when the project was initially released. So the 2018 here is correct, even though it’s no longer 2018! Also note that the video for this project is optional, you do not need to complete it if you do not want to. This is only true for this project, Project 0, and Project 7. For all other projects, a video is mandatory.

Using Git, push your work to https://github.com/me50/USERNAME.git, where USERNAME is your GitHub username, on a branch called games50/projects/2018/x/angry or, if you’ve installed submit50, execute
```
submit50 games50/projects/2018/x/angry
```
instead.
Record a screencast (if you want), not to exceed 5 minutes in length (and not uploaded more than one month prior to your submission of this project) in which you demonstrate your app’s functionality. Upload that video to YouTube (as unlisted or public, but not private) or somewhere else.
Submit this form.

You can then go to https://cs50.me/cs50g to view your current progress!