Abstract
This article analyzes the contributions of a collaborative workshop to the validation and improvement of Matematicards, an educational card game developed in a Mathematics teacher education program. This qualitative, descriptive-analytical experience report draws on records from a two-hour activity held in September 2026 with 13 undergraduate students at the Center for Higher Studies of Parintins, Amazonas State University. Eleven students played in two groups, while two acted as mediators and documented occurrences. Direct monitoring and written records focused on the educational resource, its rules, and its operation. In the initial rounds, color matching prevailed over solving the mathematical challenge printed on the preceding card. The teacher in charge therefore proposed that the challenge be answered before any discard. Correct answers allow a compatible card to be played by color or equivalent mathematical result; incorrect answers require drawing one card and passing the turn. A player who answers correctly but has no compatible card passes without drawing. A calculation sheet and an auxiliary set of challenge cards were also accepted as improvements, although the latter still requires development and testing. The experience showed that collaborative playtesting can reveal inconsistencies between educational purpose and the mechanics of the material, support clearer rules, and engage prospective teachers in the analysis, adaptation, and improvement of educational resources, without providing evidence of learning gains.