The ??? badge in Tower Defense Simulator is the hidden-wave achievement badge, and the wiki lists its requirement as Triumph Hidden Wave on any Regular Map. The badge name is shown as ??? with no description available, which matches why guides often refer to it as the hidden badge.

How to get it

  1. Enter a Regular Map in TDS.
  1. Trigger and clear Hidden Wave successfully.
  1. Finish the match to receive the badge reward.

What to know

  • This is an achievement badge , not an event badge, so it is tied to a specific in-game challenge rather than a limited-time event.
  • The badge is rare compared with standard mode completion badges, which is why many guides treat it as a special unlock.

Quick note

If you meant a different “??? badge” from another TDS version or roleplay game, the badge list is different there, and the exact method can change.

TL;DR: Beat Hidden Wave on any Regular Map in Tower Defense Simulator to get the ??? badge.