Sentinel is a side-scrolling action game where several worlds have been invaded by aliens, and it's up to you to free them. A glowing orb called the Sentinel has been sent to absorb the alien energy. As it floats above the scrolling landscapes, you need to protect it from enemy attacks using the light gun to destroy enemies and enemy fire. If you fail to destroy an enemy, its energy supply will deplete, destroying the Sentinel . The game features four levels of increasing difficulty, each with a large boss at the end. Bonuses can be encountered to give you increased firepower and energy.
The gameplay involves navigating through the scrolling landscapes while protecting the Sentinel from enemy attacks. You need to use your light gun to destroy enemies and enemy fire before they harm the Sentinel . The game features three levels of difficulty, allowing you to choose how challenging you want the experience to be.