Plain Sight is fast-paced and the gameplay mechanics are easy to learn, well thought and provide instant fun. The controls are very smooth: no mouse lag, nor mouse acceleration, nor any stupid things like that (I'm tired of horrible console ports that suffer from these kinds of issues). The music fits the game nicely and it's refreshing to hear something different (jazz should be used more often in video games). Unfortunately, there's no music in-game, only in the main menu. Graphics-wise, it's simple (grey geometrical forms) but pleasant to watch and the lighting effects are eye-candy. The UI is small and clean so it doesn't prevent you from seeing what's going on.
If I had to choose 2 words to describe Plain sight, it would be "simple" and "fun".