Sensible Train-Spotting

A small man in an anorak with a Thermos flask sits on a bench by some busy train lines and notes down the train numbers as they go. All the joy (?) of trainspotting but from the comfort of your computer, your task is to tick off the numbers of various trains as you see them come past your position. The game difficulty increases as you progress, to a point where there are 16 train numbers to tick off and five train lines in front of you, with everything masking everything else. It's got nothing whatsoever to do with football.