How to initialise and use array in game assignment

Processing Coding Questions
10

Next, what we really want is for our invaders to start off the right edge of the screen and move towards the left. You may have noticed that when I drew the invaders, they are spaced 70 pixels apart and they all have an offset in the x direction of 0.

If we change this 0 to something else - a variable that controls how far along they are, they will all move together, but kill 70 pixels spacing. Actually, since we are drawing multiple things at this position, it makes a lot more sense to use translate(), like so:

int[] invaders;
float offset;

void setup() {
  size(800, 300);
  invaders = new int[800/35];
  for ( int i = 0; i < invaders.length; i++) {
    invaders[i] = 6;
  }
}

void draw() {
  background(0);
  offset = mouseX;
  // Draw all invaders.
  for ( int i = 0; i < invaders.length; i++) {
    if ( invaders[i] != -1 ) {
      rectMode(CENTER);
      pushMatrix();
      translate(width - offset + i * 70, height/2);
      fill(255);
      rect(0, 0, 40, 40);
      fill(0);
      text(invaders[i], 0, 0);
      popMatrix();
    }
  }
}

Run this and verify for yourself that changing the mouseX amount changes the offset variable which controls where the invaders are drawn. Now we change the offset variable a bit, and it looks like our invaders are moving in from the right:

int[] invaders;
float offset;

void setup() {
  size(800, 300);
  invaders = new int[800/35];
  for ( int i = 0; i < invaders.length; i++) {
    invaders[i] = 6;
  }
  offset = -70;
}

void draw() {
  background(0);
  offset++;
  // Draw all invaders.
  for ( int i = 0; i < invaders.length; i++) {
    if ( invaders[i] != -1 ) {
      rectMode(CENTER);
      pushMatrix();
      translate(width - offset + i * 70, height/2);
      fill(255);
      rect(0, 0, 40, 40);
      fill(0);
      text(invaders[i], 0, 0);
      popMatrix();
    }
  }
}
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