Glad you enjoyed the game! ;)
It took three months (working on mornings, lunch breaks, evenings and weekends) to make the first released version, and another three for the final one (with a thankfully more leisurely pace). That being said, I had most of the tech and tools ready when I started, and had done a few similar prototypes in the past (some enemies are lifted straight from them). Also, I had a soft deadline that helped me scope small and keep me focused and on track, which helped.