22. case 20 Space Shooter¶
22.1. Step 0： Pre Build Overview¶
In this project, we will create a simple space shooter game where you have to try to shoot and avoid falling projectiles.
1 x BBC micro:bit
1 x Micro USB cable
1 x Breakout board
1 x ADKeypad
Learn to use the ADKeyboard.
Learn basic game programming.
22.4. How to Make¶
Step 1 – Components¶
First of all, plug in the ADKeypad. Ensure the colours match and take note of what pin you plug them into as it will be relevant later.
Step 2 – Coding¶
At the beginning of our code, we will need to initialise the variables we will use: playerscore for the current player’s score, noalien as a storage of whether or not there are aliens currently on the screen, hi for the current highscore, gamestart to keep track of what state the game is currently in, destroyedpos as an array to store where the player collided with an alien, shots to store the position of the shots that the player has shot, aliens to store the positions of the aliens, pos to keep track of the player’s current position, toprow to store if there is an alien currently in each position of the top row, as well as a few temporary variables. We will need to use all these variables later.
This function, unrendership, turns off the LEDs that represents our spaceship. We will use this to move the spaceship around.
This function, rendership, turns on the LEDs that represents our spaceship. After using unrendership, we can update the player’s position then use rendership to change the spaceship’s position.
This function, unrendershots, turns off the LEDs that represents the player’s fired shots. Similarly, we will use this function to update the positions of the shots.
This function, rendershots, turns on the LEDs that represents the player’s fired shots. Similar to unrendership and rendership, after using unrendershots, we can update the shots’ positions then use rendershots to change all fired shots’ position.
To start the game, we detect if the player pressed the “A” button on the ADKeypad and the value of gamestart is 0. If so, we set the value of gamestart to 1 to signify that the game has started, reset the player’s position to the centre, set the player’s score to 0, turn off all the LEDs on the screen then render the ship using the function we made earlier.
Finally, if the value of gamestart is 1, the player is currently playing the game! At the start of each loop, we turn off the LEDs of each shot the player fires, since they need to move upwards by 1 position. We use the Math.random() function to randomly determine if we should spawn an alien this frame. You can lower the number to make game harder, or increase the number to make it easier. Here, the value we use is 15, which means that there is a 1/15 chance that an alien will spawn every loop. However, we need to check that the top row of the column we want to spawn in is not occupied, or there will be overlapping aliens! Next, we loop through the aliens and move them downwards by 1 position every 5 times the forever loop runs. If an alien enters the top row, we set the value of toprow of that column to 1, and if an alien leaves the top row, we set it to 0.
Then, we check if each alien is outside the screen, and, if it is, we remove it from our aliens array. Lastly, if there are no aliens on screen, we spawn an alien in the same was we would if it spawned from the 1/15 chance.
After updating the aliens’ positions, we check for collisions, then update the shots’ positions. Then, we spawn a shot if the player pressed the D button on the ADKeyboard. After that, we remove any shots which are outside the screen.
Finally, we check if the player has pressed the C or E keys on the ADKeyboard, and update the ship’s position accordingly. After that, we render the shots that the player has fired, then set a pause of 0.08 seconds per loop so that the game advances at a playable speed.
For the whole program, you can download directly from the link below：
Or download from the page below.
Step 3: Using It¶
Playing the game is very simple. Just use the A button on the ADKeyboard to start the game, use the C and E buttons to move and the D key to shoot the aliens!
Step 4 – Success!¶
Voila! Time to have some old fashioned arcade fun with your new space shooter. What highscore can you reach?