Shadow Duel is a survival game split into two halves of the screen. You control a character on the left side; your Shadow mirrors your movement on the right using one of five mirror modes — Normal (left-right), Horizontal (up-down), Vertical (inverted), Diagonal, or Chaos (random offset). You take damage from obstacles; your Shadow is invincible and destroys any obstacle it touches, earning you bonus score and coins.
Obstacles spawn and move across the full arena: spikes, wall blocks, rotating blades, laser beams, and drifting mines. Survive as long as possible across escalating difficulty levels. Power-ups appear every 5 seconds: Shield, Speed Boost, Stun (freezes the shadow for 3 seconds and awards bonus score), Score Boost, and Heal. You have 3 HP. Unlock new skins in the shop.