Everyone wants to be happy, so why don't you make a regular glass happy. For complete happiness, he just needs to be filled to the brim with clean water. Open the tap, it is at the top of the screen and let the water flow, but do not overflow, the dotted line will show you the border that you should not go beyond. As long as you press the button, the water will flow, and if you release it, it will stop. This is convenient, because at subsequent levels between the tank and the source, various obstacles will appear and the supply of water in parts will be just in time. The glass will quickly cheer up as soon as it fills with liquid, do not upset it by wasting water. Be nimble and skillful, and it doesn't bother you to think before you start the next level and turn on the tap in Smiling Glass.