A mobile football game’s computer-controlled opponents became significantly harder for players who repeatedly dismissed purchase offers, according to a study published on Friday. The result puts RivalPitch Mobile under scrutiny on the first day of Brazil’s Digital Play Fairness Act, which requires publishers to disclose when paid offers influence gameplay.
Researchers compared 12,600 matches played by 1,200 consenting participants in a controlled test, holding teams, tactics and match histories steady. After players dismissed three offers for a R$39.90 (about €6.50) training pack, opponents pressed more aggressively in 62% of subsequent matches, compared with 31% in the control group, the paper reports.
The difficulty shift
The new law applies to games with paid digital items and takes effect across Brazil on Friday. Publishers must tell players when purchase history affects difficulty and provide a setting to turn off that personalisation. The federal Digital Services Secretariat can demand technical records and impose fines of up to R$22 million (about €3.6 million) for serious or repeated breaches.
Diego Ramón-Murillo, a computer scientist at the fictional Instituto de Integridade Digital and a co-author of the study, said the team repeated the test across six phone models and two game modes. “The players did not get worse. The opponent’s behaviour changed after the offer was refused,” he said. The paper’s authors say the pattern persisted when they swapped teams and reversed the order of matches.
The players did not get worse. The opponent’s behaviour changed after the offer was refused.
Diego Ramón-Murillo, study co-author
Publisher disputes the result
The game’s publisher, Northstar Playworks, said the study mistook ordinary adjustments to match difficulty for a response to purchase choices. In an email, product director Manuela Ebner-Binder said the game reacts to match results and tactical settings, not whether a user buys an item. The company said it would review the researchers’ methods and publish details of its own testing.
Rega Erna, a policy adviser at the Digital Services Secretariat, said the law does not ban changing an opponent’s behaviour; it requires firms to explain what triggers the change and give players a meaningful choice. The office expects publishers to submit their first compliance reports within 30 days. It has not said whether it will open a formal review of RivalPitch.
The researchers say their test cannot show how often the same pattern occurs among the game’s full player base: they did not have access to the publisher’s server data. But their controlled results raise the possibility that two people playing the same mode could face different challenges because one declined an offer. Northstar Playworks said it had not seen evidence of that happening outside the test.
The study was released as players in São Paulo and Brasília began receiving the game’s latest update, which adds a new player-versus-computer mode and more tactical controls. Its authors are asking the publisher to let an independent team repeat the experiment using anonymised gameplay records. Under the new law, the company must explain its personalisation settings to Brazilian users by 25 October.
