How do I change the font, line spacing, background, or brightness?

In the app:

1. Open any book and tap the middle of the screen
2. Tap the “A” icon (“aA” on Android) in the pop-up menu
3. Change the settings you want to (font size, background color, etc.)

On the website:

1. Open any book and move the cursor to the upper right corner of the screen
2. Press the “Aa” icon in the pop-up menu
3. Change the settings you want to (font size, background color, etc.)