Lab 3: Space Invaders (No Sound)

Objective

Write the software that implements all video functionality for Space Invaders. Your game should closely mirror the game shown in the video below.

Team Git Repository

This is the only lab where you will be permitted to work in a team of two. You will use a shared repository for this lab, and then return to working in your private repository for the remainder of the labs.

Follow this link to create a new shared Github repository for lab 3: https://classroom.github.com/g/RZersSOA

  • The first team member to sign up should create a new team name.
  • The second team member can join the team created by the first team member.

Once your empty lab 3 repository is created, use the Import Code button to import the code from one your your repositories. You can choose which member of team’s code to use, but both team members must have submitted lab2 before you share your code.

Implementation

Milestone 1

Part A

Write a document describing your software organization. You can use this document as an example. Submit your document via Learning Suite.

Part B

Complete the end scenario for space invaders. See the video above for details on how it should function (fast forward the video to 3:20). Note that the video says the high score screen can be in any pattern or configuration, meaning you can have as many rows or columns of scores as you like and the button API can be however you would like to implement it, as long as it matches the video’s functionality. However, it is required that the high scores are presented in sorted order from highest score to lowest and that at least two text sizes are used. Refer to the HDMI page for documentation on how to interact with the hdmi driver.

Note: To make it easier for the TAs to grade this, you should commit an existing high scores file into your repository. Make sure not to use absolute file paths when opening the high-scores file, as the paths will likely be different on the TA’s grading system. You should also not rely on your space invaders executable being run from any particular directory. Instead, access your high scores file using a path relative to the space-invaders executable. Stack overflow has a good explanation of how to do this with the readlink function.

Milestone 2

Implement all of the game video except for bullets and collisions. Tanks should move, aliens should march, etc. Use the video above as a reference. Keep in mind that when an entire column of aliens is gone from the edge the remaining aliens keep marching to the edge of the screen, past where the would have stopped if the edge aliens were alive. This feature doesn’t need to be functional for this milestone, but keep it in mind for the next milestone.

Milestone 3

Implement all of the game video, including bullets and all game interactions. When you have finished this milestone, you will have the entire game implemented minus sound. Use the above video as a reference.
It is difficult to see, but the number of points added to the score for each saucer destroyed is a number between 50 and 300, in multiples of 50. Also, the points for the block aliens are 10, 20 and 40, starting from the type on the bottom row and going up to the type on the top row.

Requirements

Unlike previous courses, in this course you are given quite a bit of freedom regarding your implementation strategy. However, you must work within these requirements:

  • You must adhere to the coding standard.
    • Since header files are usually provided to you, students often forget about the coding standard rules regarding header files. Be sure to review Rule 2.1.
    • You will find it easier to follow this rule if you only put items in your header files that need to be used by other .c files. If a #define, struct, etc. is only used in one .c file, it should be placed at the top of that .c file, and NOT in a header file. This is good C coding practice and you should make a habit of following it when designing your own software structure.
  • You must use state machines as you learned in ECEn 330 and ECEn 390. Your game loop will consist only of calls to the tick functions for each of your state machines. All game interactions are performed directly by state machines (either as Moore or Mealy actions). As with the coding standard, the TAs will inspect your code to ensure that you adhere to this requirement.

Submission

Follow the submission instructions for each milestone on the Submission page.

Resources

An Example Approach for Alien Bit-Map Data

There are several ways to implement the bit-maps for your aliens. In the past, students have used editors to create bit-maps. Another approach is to create the bit-maps using a text editor. The code below will not compile but should give you a good idea of how to do this. There is more code further down that contains all of the bitmaps you will need for this lab in text form, as will be explained.

If you squint your eyes a bit, you should be able to see the shape of one of the aliens in the text below (the 1s are the bright pixels that form the alien). Carefully study what packWord32 does. Also, note that the 1’s and 0’s that form the alien are part of a ‘C’ array initialization. After thinking about this for a bit, you should be able to figure out how use this data structure to write the bit-map to the display.

const uint32_t sprite_alien_bottom_in_12x8[] =
{
	packWord12(0,0,0,0,1,1,1,1,0,0,0,0),
	packWord12(0,1,1,1,1,1,1,1,1,1,1,0),
	packWord12(1,1,1,1,1,1,1,1,1,1,1,1),
	packWord12(1,1,1,0,0,1,1,0,0,1,1,1),
	packWord12(1,1,1,1,1,1,1,1,1,1,1,1),
	packWord12(0,0,1,1,1,0,0,1,1,1,0,0),
	packWord12(0,1,1,0,0,1,1,0,0,1,1,0),
	packWord12(0,0,1,1,0,0,0,0,1,1,0,0)
};

One of the requirements is for the sprites to be scaled to be the same size as in the video. Using this suggested implementation, it is easy to dynamically scale the sprites when they are being displayed.

Note: the function provided below may not be exactly what you want to use in your game code. It is provided to see how you actually interpret the packed words.

Alien Shapes Defined in C Code

To save some time, we will give you the definitions of the aliens in their two guises, the spaceship, etc. These definitions are useful if you use the approach that was discussed above.

Bunker Erosion Patterns

The patterns for the bunker erosions are depicted in this pdf file. By studying this file and watching some of the provided game videos, you should be able to figure out how to code the bunker erosions. If you watch the game carefully, you will see that the bunkers are composed of blocks that go through predictable patterns as they are hit with bullets.

bunker_damage.pdf

The corners of the bunkers should erode such that no pixels get set that weren’t set before they started to erode. So, although the erosion patterns are square in shape, the corners of the bunkers should erode within their original pixel constraints.