Creating a Progress Bar GUI

Preparing the Progress Bar Image

Prepare a bar to indicate progress and a background bar as shown below, and upload them to My asset.
Then add them to the scene as GUI objects.

Placing the Images

Place the GUI objects added to the scene to overlap as shown below.

Setting GUI Object Properties

Set the X value of Transform -> Center in the properties of the progress bar GUI to 0.

This will make the center of the progress bar GUI align with the left edge.
So, as shown below, when the X size decreases, it starts decreasing from the right.
When the size increases, it extends from left to right.

Next, adjust the scale of the progress bar to find the maximum X value when the background bar is fully filled.
Remember this maximum X value.

Writing the Code

Write the code to change the progress of the bar based on certain conditions.
In this snippet, we wrote the code to increase the progress when the player collides with an item.

const MAX_LENGTH = 48; // Enter the maximum X value noted earlier here
const ITEM_AMOUNT = 5; // Number of items
 
const progress_bar = GUI.getObject("progress_bar");
let score = 0;
let items = [];
 
for(let i=1; i<=5; i++){
    items.push(WORLD.getObject("item" + i));
 
    items[i-1].onCollide(PLAYER, function() {
        items[i-1].kill();
        score++;
        progress_bar.size.x.value = score / ITEM_AMOUNT * MAX_LENGTH; // Increase the size of the progress bar each time the player collides with an item
    });
}