DD Wrecker is the first mini-boss in Sonic Mania, encountered at the end of Green Hill Zone Act 1. It is based on the original Green Hill Zone's boss.
The attack pattern of this boss is relatively predictable. It acts similarly to the original boss, swinging a ball back and forth. One of the balls will be orange at all times - you cannot hit it when it is in this state. Over time, the two balls will change states. After a few seconds, the balls will return to normal state swing quickly in a circular motion in the middle of the level, before repeating the previous pattern again.
Once one of the balls is destroyed, the remaining ball will start a new attack pattern - it will fly to either side of the level, and bounce across the ground to the other side. You can hit the boss only when it is in its normal state. Each ball takes 3 hits to destroy, and when both are destroyed, the boss ends.