This week we carried on our “Shootah” space shooting game  by adding some bullets with an appropriate sound effect.  This brings the game to the stage shown below:

Not very snazzy but it’s starting to show some promise!

As with last week, this will only run if served up from a web server, we had a few ninjas in that missed last week and had to install node.js and local-web-server application.

Bullets!

Our Bullets were a pretty simple object that just moves up constantly – this has the following code:

class Bullet {
    constructor(x, y){
        this.x = x;
        this.y = y;        
        this.speed = 10;
    }

    move(){
        this.y = this.y - this.speed;
    }

    show(){
        push();
        fill("yellow");
        ellipse(this.x, this.y, 10, 10);
        pop();
    }
}

function preload(){
   playerImage = loadImage("images/spaceship.png");
   bulletSound = loadSound("sound/laser.mp3");
}

function draw() {
  // .... skipping a few lines
  for(let i=0; i< bullets.length; i++){
     bullets[i].move();
     bullets[i].show();
  }
  // .... skipping a few lines
}

function keyPressed(){
   if(keyCode==UP_ARROW){
   bullets.push(new Bullet(player.x, player.y));
   bulletSound.play();
 }
}

The sound was done very similarly to the image – we created a folder (sound) and added a sound file we found on the internet to the folder.  In the preload function we loaded the sound from the file into a variable (“bulletSound”).  In the keyPressed function, we check if the pressed key is UP ARROW and if so, we play the sound and add a new bullet to the list.. voila!

Problems to work on!

A great start but a lot left to be sorted with this game!  Here are some of the items:

• The bullets array grows forever – this really starts to slow down the game as we keep playing it.  We need to add some code to remove a bullet from the array when it is gone off the screen.
• The player has no edge detection – we need some way to keep it onscreen.
• We need some enemies!!
• We need to get the bullets to check when they are hitting the enemies!
• We need to keep and display a score
• We need a way to die.. perhaps the enemies can drop bombs?
• Other ideas:
  • Maybe a background tune in a loop?
  • Maybe a scrolling starfield in the background?
  • Maybe multiple levels?
  • Maybe different types of enemies?
  • Maybe a shield?
  • Perhaps some different weapons or weapons you can pick up?

We have gotten this far so we might as well push forward and make this a fully working game so we’ll get some of the above sorted next week!  The code is as usual up on our github.  https://github.com/coderdojoathenry/creators2018

We welcomed back Hackers Group members Luke and Sean, who had projects at the Young Scientists Exhibition last week.  Details of their projects are in another post: Congratulations to our members who presented at the BT Young Scientists 2019!

This week we divided the group into two teams to work on our hide-and-seek robots:  One team to build the hider robot, the other to build the seeker robot.

The two robots can use many of the same parts, but the control systems will be different.  The hider robot will be operated by a person with an RC transmitter.  The seeker robot will control itself.

Team Hider started resurrecting a radio-controlled robot that we built last year.  The robot was involved in a battle-bots battle at the end of the year, so it is in pretty poor shape.
Teem Seeker worked on a colour tracking system.  We took the code that we developed on a laptop before Christmas and tried it on two Raspberry Pis.  We found that the original model Raspberry Pi wasn’t fast enough to do the job we needed.  It took 6 seconds to acquire an image from a webcam.  We tried a Model 3 B instead.  This was fast enough for our needs.  We then started work on tuning the colour detection.  There’s some more experimentation to be done to find the best colour range to work with.

Up to this point in Creators we have been building all of our apps as sketches ourselves using the drawing functions in p5/javascript – ellipse, rect, etc.  This is great but a question we get all the time is “how can I load IMAGES and Sound into my games?”.  This week we got stuck into this, using a project of a very basic shooting game as an example.

However, before we got stuck into writing our game, we needed to install something on our computers called a web server.

What is a web server and why do we need it?

A web server is a program that makes files available on the internet.  Mostly, the files are made available to programs that can understand the Hyper Text Transfer Protocol – or http for short.  “http” probably sounds familiar – this is because you are used to seeing it on your browser before internet links.

Up until this point, we simply opened files on our computer with explorer and if you looked at the browser link you would see something like this:

file:///C:/Users/markdav/code/dojo/creators2018/Week11-shootah/index.html

The “file” at the start means the browser is opening a file on the local computer.  This works great for a lot of things, however if you write a program in javascript which runs on the computer, javascript is not allowed to open files on the local computer.  Why? Because if javascript could open files on the computer of the person opening a website, it would be easy to write a webpage that steals information from people looking at it, without them knowing it.  This would be a BIG security problem!!

Javascript can only open files which are served out by a web server – so in order to load images or sound into a javascript program, we need to make sure that they are served out by a web server.

Installing our Web Server – Node.js

There are lots and lots of web server programs out there but we decided to install one which is written in javascript – we are javascript nuts after all!  Node.js isn’t actually a web server, but is a set of programs kind of like p5 that make it easy to write or install programs in javascript for your computer – and especially ones like web servers.  Later in the year we will play some more with node.js and write our own programs in it to do some cool stuff.

We installed node.js from the node website here.

Once we installed node.js, we then installed a web server which is written in node.js – we installed one called “local web server”.  To install local web server – we opened a command terminal in the computer and typed the following:

npm install -g local-web-server

npm stands for “Node Package Manager” and it’s a program that makes it easy to install programs written in node on your computer.  Once this was done, we have a new command in our computer – the command is “ws” and what it does is to start a web server that puts the files from the current folder on the internet!

To try it out, we started a new p5 project called “shootah” and right clicked on the folder and selected “open in terminal”.  The command prompt appears directly in Visual Studio Code, which is handy.  We then typed “ws”

markdav@markdav2017 MINGW64 ~/code/dojo/creators2018/Week11-shootah (master)
$ ws
Serving at http://markdav2017:8000, http://192.168.71.1:8000, http://192.168.48.1:8000, http://192.168.1.20:8000, http://127.0.0.1:8000

This started a web server in the folder which serves out the files – to open we used either one of the links given, or actually we kind of preferred to type “http://localhost:8000” which was another way of putting it.  When we did this, the files just showed in the browser!

Developing Shootah

All this installing took us some time, but we were ready to get stuck into developing our space shooting game.  We go to the stage of getting a Spaceship which we could move left and right – but no bullets, sound or enemies, yet.

First we needed a spaceship picture, and we had a bit of fun rooting around on the internet for one.  Some people created their own images.  I ended up picking this picture (you can right-click this picture and save it if you like it too):

When we had the spaceship picture, we created a folder to store our pictures.  I created a folder called “images” and put the picture in there and called it big-spaceship.png.  Some others called their folder “assets” which is a term you often see used. To be honest my picture was a bit big – you are better off making the images just the right size, as it saves a little bit on memory for the computer when showing them.

We learned that there is another special function in p5 which is best to use when we are loading files like sounds and images into variables – it’s called “preload” and we wrote the code to load our images in there:

let playerImage;

function preload(){

      playerImage = loadImage("images/big-spaceship.png");

}

Once we had the image loaded, we could draw it using the “image” function.   The show function on our player used this to paint the image:

show(){
    imageMode(CENTER);
    image(this.img, this.x, height-100, 100, 100);
}

Aside from that, the code was pretty similar to other sketches we have done.  We put some basic code in to allow the player to be moved left and right.  This is as far as we’ve gotten – next week we’ll work on it some more and see if we can get some enemies, bullets, sounds, maybe stars, scores, better movement, etc.  Code is on github as usual!