Hard-Light Armor is special holographic armor created by Dr. Eggman using pure energy and designed for on-hands combat.
Shattered World Crisis
During the Shattered World Crisis, the Naugus twins invaded and successfully took over Eggmanland despite Dr. Eggman's efforts at kicking the two out. With his defeat, he called upon his Egg Bosses to help reclaim Eggmanland. However, he knew that Naugus needed to be dealt with personally, thus Eggman created the Hard-Light Armor and was planning to use it as a trump card against Naugus. When it came time to brawl against the Naugus twins, Eggman activated his Hard-Light Armor and used it against Crystal Sonic and Walter Naugus. After subduing Naugus, Eggman used the remaining time and power of the Hard-Light Armor to blast Naugus with an arm cannon. However, Crystal Sonic took the hit instead of Naugus, which reverted the Crystalmancy from Metal Sonic. (SU: #84, #86)
The Hard-Light Armor, despite only lasting for five minutes at the most, is able to allow Eggman to punch both Crystal Sonic and Walter Naugus at ease and without pain. Eggman is also able to create an arm cannon, powerful enough to revert the Crystalmancy from Metal Sonic, as well as being bright enough to temporarily blind anyone near the blast.
The Hard-Light Armor is a holographic, pure energy-made brawler type armor that, when fully charged, can be used only once and for five minutes. It is made from green energy that is resistant to Crystalmancy.
The Hard-Light Armor has spring-like shoulder and ankle pads, along with a helmet and torso armor piece resembling the Big Arm mecha. The Hard-Light armor covers Eggman's head, shoulders, arms, hands, torso, ankles, and legs.