In Tennis Clash’s Ace Academy, players spin a slot machine that awards new abilities for characters—but only if players land a special symbol on each of the machine’s three reels. To ensure that winning doesn’t depend entirely on luck, spins also fill a meter next to the reels that increases players’ chances of winning an ability at milestones and awards an ability when complete. Although many gacha mechanics contain some kind of mercy system, it’s rare for apps to make these systems explicit, let alone a prominent component of the UI.