I played this game many times. Quite a classic.
The aim of this game is to survive the nights fighting off zombies from our barricades. Protect the barricades and live. Survive as long as possible by making use of the time effectively, by repairing the barricades , searching for weapons, defend the barricade, find the survivors etc.
This game has some features: days and nights of game play ; about 10 or 11 total different weapons i guess ; many random enemy appearances, I have seen at least few hundreds different appearances. Controls are simple, using keyboard and mouse to aim & fire and move, good for spending the time while boring. ESC to open options and pause. This was one of the oldest shooter flash game i guess. But I still play it sometime on the browser.
One of the nice feature of the game is that 20 days and nights of game play. sometime after day 11 something it's possible to lose if you didn't prepare well in the day time. It's a good defense game.
umm the bad thing or down side of the game probably is that you just keep fighting waves of enemies. There is no "assault" or "offense". There is only "defense" and "survive". But still, it's quite fun and classic. Also there is no bugs and no game crashes even I have played a hundred times at least.
Many flash game site also have this game, hmm like armorgames.com , flashygames , kongregate etc. It's still quite good for spending some spare time. Running around shooting zombie :)