MIPS汇编代写 COMP2611 Computer Organization

COMP2611 Computer Organization, Fall 2018

Programming Project: The Space Invaders Submission deadline: 11:55PM, Dec 1 (Sat), CASS

1. Introduction

In this project, you are going to implement a Space Invaders game with MIPS assembly language. Figure 1 shows a snapshot of the game. The evil aliens are invading your space base so the spaceship needs to wipe them off. The spaceship emits bombs to kill aliens. Player needs to shoot and kill all aliens before they reach to your space station.

Figure 1. The snapshot of the Space Invaders.

2. Coordinate System

The game screen is of 800-pixel width by 600-pixel height as illustrated in Figure 2. The top-left is the origin of the coordinates, denoted as (0, 0). The value of x-axis increases from the left to the right and the value of y-axis increases from the top to the bottom. This follows Java Swing coordinate system, which is used to support GUI in the game.

All game objects are with images of rectangular shape. Top left coordinate of each object is used to represent its location. For example, the alien in Figure 2 is at position (200, 120).

3. Game Objects

There are four types of game objects: Spaceship, Alien, Simple bomb, and Remote-control bomb. Every object has attributes as listed below. You can manipulate the attributes through appropriate syscall services (details in Section 6).

Figure 2. The coordinate system.add a rectangle

 Current location: the top-left (x, y) coordinate which indicates the current location of the object.

 Speed: the integer variable for the moving speed of the game object.
 Direction:aBooleanvariableforthemovingdirectionofthegameobject.Spaceshipandalien

move from left to right when it is TRUE, from right to left otherwise. Bomb shoot by Spaceship always moves upwards. The next location of the Alien depends on its current location, moving direction and moving speed. The next location of the spaceship depends on the input of player.

 Hitpoints(HP):theintegervariableindicatingthelifevalueofagameobject.Ifthehitpoint of an object goes to zero, then the game object is dead. Aliens have initial hit point of 20. Both types of Bomb and Spaceship have the hit point of 1.

Table 1. Properties of game objects.

4. Game Details
4.1 Winning and losing of the game

The game has four levels, with increasing number of aliens in each level, i.e. 6 aliens in level 1, and 3 additional alien for each higher level. The player wins in a particular level when he/she kills all aliens and promotes to next level. The player wins the game when he/she passes all levels.
The game terminates and player loses when there is an alien who touches the bottom of the game screen (i.e., y-label of the alien exceeds 420).

4.2 Bomb and Hit

Bombs are emitted from the spaceship, moving upwards at the constant speed of 6. There are two types of bombs: simple bomb and remote-controlled bomb.
Simple bomb is active once it is shot. Remote bomb is initially not destructive until it is activated by the player. Pressing the key ‘ ’ (white space) emits a simple bomb . Pressing the key ‘r’ emits

a remote-control bomb bomb and it is shown as

which is inactive. Pressing the key ‘a’ afterwards activates the remote .

Bomb kills Alien b) Bomb hits multiple objects Figure 3. Different scenarios of bomb hit

a)

As illustrated in Figure 3(a), suppose an alien currently locates at (x, y) on the screen. If a simple bomb or an activated bomb intersects with its central area, the area which locates at (x+35, y) with 10-pixel width and 40-pixel height, the alien is killed and its hit point is reduced to 0. Game score increased by 20. A dead alien’s ID is updated to 0 (a flag that helps to check whether an alien is alive or dead.) The explosion of the bomb also destroys itself; therefore, its hit point is reduced to 0. Please note a bomb may cause damages to two aliens simultaneously when it happens to intersects with center of both.

For each level, there are 2 simple bombs and 1 remote-controlled bomb for player to use. bomb_count records the number of bombs that are currently flying. If bomb_count equals to 2, the player are temporarily banned from shooting simple bombs. For the remote-controlled bomb, if rbomb_count is 1, the player cannot shoot the remote-controlled bomb too. The number of bombs available to use is shown on the top left of the game screen.

4.3 Alien

Game level 1 has 6 aliens, in two rows, with ID 2, 3, and so on. All Aliens move horizontally at constant speed of 6. When touching the border, all Aliens go down 20 pixels. During the game, if the alien is destroyed by the bomb, its ID will be set to be 0.

Promotion to the next level of game will increase the number of alien by 3, speed by 3 and re-create all the aliens. Alien_num saves the number of Aliens in current game level. Array Alien_ids saves IDs of Aliens, starting from 2, 3, 4 until 2 + Alien_num – 1.

4.4 Game initialization

At the beginning of the game, the number of Aliens is 6 (2×3) and the numbers of simple bomb and remote bomb are 2 and 1, respectively. The following levels of the game run quite similar to the level 1, with more aliens fly with higher speed.

4.5 Game skeleton

The game runs as a big loop. Each loop print out a static game screen with all game objects. By properly set the time interval of game screen print, we can create an ‘animated play’ of the game. It proceeds as follows:

1. Get the current time: jal get_time.
2. Check whether the game reaches the ending condition: jal check_game_level_status checks whether the user wins/loses/continues the current level. Then jal game_end_status handles different actions for game lose, game win or promote to next level. If the player is still in the middle of the game, go to step 3.
3. Update the game object’s status: jal update_object_status. Check the game objects’ status. Destroy any killed aliens or exploded bombs with syscall 116.
4. Process the keyboard input from player: jal Process_input. The input key is stored using the Memory-Mapped I/O scheme. If the keyboard input is valid, perform the related action.

5. Check bomb hits: jal check_bomb_hits: One-by-one, for each active bomb, check whether it hits any aliens by jal check_one_bomb_hit. If any hit happens, update the status of alien, and the bomb.
6. Move the aliens: jal move_Aliens.
7. Move the bombs: jal move_bombs.
8. Update the score: jal update_score.
9. Refresh the game screen.

10. Take a nap if necessary: jal have_a_nap. The interval between two consecutive iterations of the game loop is about 30 milliseconds.

11. Go to step 1.

5. Your tasks

Read the skeleton code and understand how it works. Then implement the following MIPS procedures in the skeleton code.
Note: You don’t need to understand every single detail of the skeleton. You can discuss with your friends if you have difficulty in understanding the skeleton. But every single line of code should be your own work.

Note: The skeleton file provided is just to help you understand the game thoroughly and ease your life. If you think it poses any restriction on you, feel free to have your own implementation from scratch. If you don’t use the skeleton code, please state that at the beginning of the submitted .asm file.

6. Syscall services in usage

We have implemented a group of additional syscall services to support game related functions (e.g. GUI and sound). You should do your coding work with the modified Mars provided.
Syscall code should be in $v0 before usage.

7. Submission

You should *only* submit the file comp2611_game_yourstudentid.asm with your completed codes for the project. Please write down your name, student ID, and email address at the beginning of the file.

Submission is via CASS. The deadline is a hard deadline. Try to avoid uploading in the last minute. If you upload multiple times, we will grade the latest version by default.

8. Grading

Your project will be graded on the functionality listed in the game requirements. Make sure your code can be executed properly in the modified Mars.

9. Bonus

Everyone needs to finish the tasks as described in the project description.

But if you enjoy MIPS programming, and would like to make the Space Invader more fun, feel free to discuss your idea with your course instructor. With the pre-approval and successful implementation of additional functionalities as planned, a bonus of up to 2 marks (out of 100 marks of course final score) will be assigned.

You may also propose your own game. Again, discuss with course instructor for pre-approval. A good game with reasonable complexity can also earn 2 marks bonus (out of 100 marks of course final score). Note you might need to modify the Mars and design your own syscall to support the new game.