Moving the artboard
The camera in Pixly works similarly as the one in Google Maps. You can drag the screen with two fingers to move the artboard around, and if you pinch these fingers, you'll be able to zoom in and out. The zoom is limited such as you can't get the image smaller than 2x.
As easy as pie. Just drag the screen with one finger, and your tool will be applied in that area. If you want to cancel the operation, touch the screen with a second finger before lifting the first. This is not a bug, it's a feature.
Some tools work with a single touch, instead of a drag, like the Magic wand and the Paint bucket. While some others work by touching the screen several times, as placement, like the Arc, Curve and Polygon.
There are two colors in pixly, the primary and the secondary. Both are shown in the bottom-right corner, and you can touch them to expand the Color and brush. Touching one of the colors again and you can enter into the Color selector, where you can edit the current color and them check the top two colors. Touch the left color to revert it or the right color to accept the changes and continue.
You should really read about primary and secondary colors, since it's of great importance that you understand it.
The default brush is 1x1 pixel and totally solid. The brush affects a lot how your tools will look like, so you must always be aware of what it is like. You can access the brush settings by going into the Color and brush in the lower-right corner, then hitting the top-most option that shows, the Brush settings.
The ultmost shortcut here, is that you can change the brush size without going into the brush settings. You just gotta touch the screen with THREE fingers (like making a circle with your thumb, index and middle fingers) and expanding or contracting them.