Make a sprite grow and shrink

Combine repeat and changeSize inside a forever loop to create a smooth pulsing animation.

whenGreenFlag(() => {
  forever(() => {
    repeat(10, () => {
      changeSize(5);
      wait(0.05);
    });
    repeat(10, () => {
      changeSize(-5);
      wait(0.05);
    });
  });
});

The sprite grows by 5% ten times, then shrinks by 5% ten times — back to its original size — and repeats forever. Adjust the numbers to change how big it gets and how fast it pulses.

Note

changeSize works in percentages relative to the sprite’s original size. Starting at 100%, ten steps of +5 brings it to 150%, and ten steps of -5 brings it back to 100%.

Try this next

• Animate a sprite with costumes — combine size changes with costume switching for a more dramatic effect
• Repeat an action — learn more about how repeat works

Functions used

• whenGreenFlag — run code when the green flag is clicked
• forever — repeat a block of code indefinitely
• repeat — run a block of code a fixed number of times
• changeSize — change this sprite’s size by an amount
• wait — pause the script for a number of seconds

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