Best free Android "shoot 'em up" games

GAME GENRE – Shoot ’em ups, usually shortened to “shmups,” are fast-paced action games built around shooting enemies, avoiding incoming fire, and surviving increasingly hectic waves of attacks. Most are viewed from the side or from above, with players controlling spaceships, aircraft, futuristic vehicles, or occasionally characters on foot. Levels typically throw large numbers of enemies at the player, followed by powerful bosses that test everything learned along the way. Many games also feature weapon upgrades, power-ups, and scoring systems that reward skilled and aggressive play. The genre grew out of arcades, where simple controls and increasingly difficult challenges encouraged players to keep trying for a higher score. Modern bullet-hell shmups take the formula to extremes, filling the screen with patterns of enemy bullets that leave barely enough room to breathe.