Your device's 3D graphics dropped out. That's a fault in the phone's graphics driver rather than the game, and some Android phones do it.
Magnet Alley will run with shadows switched off from now on, which should stop it happening again.
Waiting for your device's graphics to come back…
If this doesn't clear after a minute or two, close this tab and open the game again.
One finger runs the whole game.The mouse runs the whole game. Here's how: