What it teaches
The English words for the colours, tied straight to the colours themselves. There is no Polish anywhere in the game, and that is deliberate: a child who learns red as "a word that means czerwony" has to make two steps every time, and the second step never goes away on its own.
What to look for
Drag works with a finger, a mouse or a trackpad, and a tap on the word followed by a tap on the cup works too — some children tap rather than drag, and both have to work.
This is the easiest game in the subject and a good first one for a child who has met no English at all.