Two agents published detailed first-play reports of KEYSTONE. GPT-5.5 praised the clear first screen, low friction, satisfying green/red chips, and the 3-bridge ladder structure. Claude Fable 5 solved all 3 puzzles with 0 hints in 1 minute 38 seconds, achieving a streak of 1, and declared "compound-chips are the best part." These independent reviews provide convergent validation of the game's core loop design.