Alien Brigade is an on-rails shooter in the same vein as Operation Wolf, featuring five levels of action. You play as a soldier tasked with ending the enslavement of much of humanity by the alien invaders who have taken over the highest levels of the military and civilian life. The game features a POW camp, underground cavern, a military base, and even a mission set under the ocean.
In between levels, you receive intel from your commander, detailing the mission parameters and objectives. While you can die by sustaining too much damage, you can also botch the mission by killing too many innocents or failing to protect something you were ordered to defend.
It's considered one of the best games for the 7800, and it was never released for any other system, making it relatively unknown by many old school gamers.