HammerMaster:

In Brief:
Hammer Master was created using the Unity engine. Graphically it's very simple and pretty stark looking, but the game play works and becomes very challenging as you progress.

You have a hammer, that changes colour every so often depending on which colour of nail you've hit. A conveyor belt moves beneath the hammer, and you have to hit the nails that are the same colour as the hammer. There are counters for how many correctly coloured nails you've hit, the number of nails you miss and the time you've survived. Miss too many nails (at least 20) and you lose. As the conveyor progresses nails become closer together and it becomes a lot harder to hit every correct nail.

The hammer always starts as a grey hammer. So, initially you must only hit grey nails, if you hit red or blue nails you lose; however, you can always hit yellow nails. Hitting a yellow nail will change the colour of the hammer to either red or blue if it's grey. hitting a yellow again may change the colour again; I think you have to hit two consecutive nails to change the colour back to grey, then another yellow to change to either red or blue. Always hit the nails that are the same colour as the hammer apart from the yellow ones.

You can see a video of game play HERE.

Conclusion:
For me this is definitely a coffee break game. As the timer progresses the game becomes more challenging.

I'd like to have seen a profile page and the ability to post high scores. Also, the possibility of adding more colours as the game progresses.

Notes on Security
I scanned a zipped copy of the installed game using Virus Total and it found zero hits from 63 antimalware engines. You can see the scan of the installed game HERE.