RayofJay has given the whole game an overhaul. palette changes, complete level layout changes, enemy logic changes (AI/timers), enemy health, bullet speeds, countless timer values, Power up function, death decrements your weapon level instead of resetting it, gaining weapon upgrades allows you to do more damage now, screen repeat function to make the game longer, double digit life count, randomized enemy locations (a select few) to name a few.

Some have claimed this game is unplayably hard. Yes, it is very hard, but, once you know the secrets and tricks, it’s really not bad at all. I recorded myself completing this hack with no continues. https://www.youtube.com/watch?v=MnU5LlA1t-A&t=116s

Expect to die a lot, though. My modification that only decrements your main weapon power instead of resetting it to zero on each death is critical for this hack to be playable.

• Database match: Jackal (USA)
• Database: No-Intro: Nintendo Entertainment System (v. 20180803-121122)
• File SHA-1: 86C392A1D9A731FA48E148AFBE60AF75F918CB5A
• File CRC32: 2E52D091
• ROM SHA-1: 813E6A8BC0A502BB393F8729B1BC19836D5421A5
• ROM CRC32: 1D5B03A5