# Health Bar ## Introduction Health bars are common UI elements in games. They are similar to progress bars, so this example could be used to create either. This example explains how to create a health bar component. ## Creating the Component First we'll define the component: 1. Open Gum 2. Open or create a new Gum project 3. Right-click on the **Components** folder 4. Name the component "HealthBar" 5. Resize the **HealthBar** component so it is wider than it is tall. For example, assign `Width` to `200` and `Height` to `32`. ## Adding a Background Next we'll add a background to our **HealthBar** Component 1. Drag+drop a **ColoredRectangle** into the **HealthBar**\\

2. Select the newly-created **ColoredRectangleInstance** 3. Select the **Alignment** tab 4. Click the **Fill Dock** button\\

Fill Dock to make the background take up the entire size of its parent HealthBar component

5. Change the ColoredRectangleInstance color to black\\

Now we have a black background in our **HealthBar** ## Creating an Inner Container The HealthBar displays its current health with another rectangle. This second rectangle will be contained inside a container to provide a boundary. To add an inner container: 1. Drag+drop a **Container** onto the **HealthBar** 2. Select the **Alignment** tab 3. Enter a **Margin** value of 4 4. Click the **Fill Dock** button

Set Margin to 4, then click the Fill Dock button

Now we have a ContainerInstance with the proper margin

## Adding the Foreground Rectangle Finally we'll add the foreground rectangle which displays the health: 1. Drag+drop another ColoredRectangle onto the ContainerInstance. Be sure to drop it on ContainerInstance so that the newly-added ColoredRectangle is a child of the container 2. Click the Alignment tab 3. Set Margin back to 0 4. Click the Fill Dock button 5. Change the following values: 1. X Units to Pixels from Left 2. X Origin to Left 3. Width to Percentage of Container 4. Width to 100 Now, the Width value can change between 0 and 100 to indicate the health percentage.

## Expose Width Next we'll expose the inner ColoredRectangle's `Width` property so it can be assigned per HealthBar instance: 1. Select the inner ColoredRectangle instance 2. Right-click on its `Width` variable and select **Expose Variable**\\

3. Enter an appropriate name such as "Percentage" and click OK Now we can add instances of the HealthBar to a screen and control its fill percentage.

Percentage value updated on a ScrollBar instance

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