The Mother Blob Attacks

You're having a nice day at the beach, and suddenly black ooze falls from the sky! It turns into a giant blob monster and multi-coloured blobs come out of it! Help, bring out the Nerf guns! This is a Tower Defence Game made by my 10 year-old son for his end-of-year exhibition. The game has an easy difficulty level and takes between 5 and 10 minutes to complete. Enjoy...