Hotline Miami is a brutally difficult, brutally violent, top-down brawler and shooter. With retro, 90s-style graphics, it has something of a feel of a Sega Genesis game -- not a SNES one; Nintendo would never have let anything this violent on their platform, but Sega was edgier.
You're assigned your missions via mobile phone by strange people who wear animal masks and claim to know all about you, though you're apparently amnesiac. The story, such as it is, is a somewhat surreal one, but it's a transparently thin veneer to provide some strange context for what's simply a game of killing everyone on each stage.
You can pick up a variety of both melee weapons and firearms; it's possible to play it stealthily, sneaking up on enemies and dispatching them hand-to-hand, or simply to blast away. Enemies are alerted by the sound of gunfire, though. Additional weapons are unlocked over time, as are additional animal masks; each mask provides a special power, and you can choose among them to suit your strategy.