Here is a hack where you must coordinate 2 battle tanks at the same time to defend the base. You must be careful if you lose the one tank as you may lose the level!
Battle City (J).nes - GOODNES 3.14
CRC32: F599A07E
MD5: CD4FE2E78DF0696DBE652F02C19541A1
SHA-1: E1061C9241B06A965FB7845CB951D921ACA010EF