Sanctum 2 blends first-person shooting with tower defense on maps where you protect a core from waves of aliens. Players spend prep phases building mazes of towers and walls, then switch to FPS mode to fight directly alongside their defenses. Most people play through the solo campaign to unlock classes and perks or team up in online co-op with up to three friends, replaying maps for better ranks. The experience feels tactical and satisfying when everything runs smoothly, but late waves quickly fill the screen with dozens of enemy types, particle effects from abilities and explosions, plus the towers themselves firing constantly. Performance load spikes during these crowded combat phases, where draw calls and AI calculations increase. The game leans more on the CPU than the GPU because Unreal Engine 3 must handle enemy pathing, physics, and simulation for every unit on screen. Stuttering or inconsistent pacing makes it harder to land precise shots on weak points or react to fast-moving threats, often causing a defense to fail. Menus can also feel capped at lower rates, and older engine quirks sometimes show up as hitches on mismatched hardware. Beginner and intermediate builders commonly overbuild for this title, assuming it needs current AAA-level components. In reality, the game has modest overall demands, with resolution and visual settings adding very little extra load compared to enemy density. Before choosing parts, understand that a stable modern baseline focused on CPU strength and smooth frame delivery matters far more than chasing high-end graphics that the 2013 visuals cannot fully use.