Summary: This game was worth every penny. The reason it gets such a high rating is because I'm rating it based on "value for money". $5 USD is such a small price. With $5, you could buy yourself a plain old cheeseburger meal at a cheap fast-food restaurant that you will enjoy for around 5-10 minutes. This game may be short, however it provides great entertainment when played in short bursts.
Summary: A simple yet fun old-fashioned zombie survival game. With simple game mechanics - like upgrade your base, build turrets etc... - it was hard for this game to go wrong. For only 3 pounds it's a reasonable game. However, there is some room for improvement. The animations could use some work, they feel plastic-like and feel unfinished. But overall a good buy if you're looking for a simple shooter on a budget.