https://wccftech.com/todays-list-of-paid-apps-and-games-that-are-free-at-the-play-store-including-pirate-defender-premium-and-more/

The titles are on free for a limited time only and may go paid at any moment. If you see a price next to the “install” button on the Play Store, it isn’t free anymore. Once you download a paid title that’s free, it’s yours to keep even after the promotion ends and you can reinstall it on any other device linked with the same Google Play Store ID.

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