Blake C Interactive animation

var a;
var a = createSprite(200, 200);
a.setAnimation("frog");
var y;
var y = createSprite(500, 300);
y.setAnimation("mushroom");
var z;
var z = createSprite(500, 200);
z.setAnimation("fly");
var score;
var score = 0;
var health;
var health = 100;
function draw() {
  background("cyan");
  fill("black");
  textSize(20);
  text("Health:", 280, 30);
  text (health, 350, 30);
  text("Score:", 30, 30);
  text (score, 100, 30);
  if (health < 0) {
    background("black");
    fill("green");
    textSize(50);
    text("Game Over!" , 40, 200);
  }
  if (a.isTouching(z)) {
    score = score + 1;
    z.x = randomNumber(400, 400);
  }
  if (a.isTouching(y)) {
    y.x = randomNumber(400, 400);
    health = health + -10;
  }
  if (keyDown("left")) {
    a.x = a.x + -5;
  }
  if (keyDown("right")) {
    a.x = a.x + 5;
  }
  if (keyDown("up")) {
    a.velocityY = a.velocityY + -5;
  }
  if (a.y < 100) {
    a.velocityY = a.velocityY + 5;
  }
  if (300 < a.y) {
    a.velocityY = 0;
  }
  if (z.x < 0) {
    z.x = randomNumber(400, 400);
  }
  if (y.x < 0) {
    y.x = randomNumber(400, 400);
  }
  z.x = z.x + -5;
  y.x = y.x + -5;
  drawSprites();
}