Celestial Buffalo Slot by Relax Gaming

Numbers run across the top of the reel set: 1, 2, 3, 4, 5. Below that, a counter showing how many symbols you've collected toward the next stage threshold (visible at 0/30 in the screenshot). The whole game is built around climbing through five stages, each one unlocking a different mechanic, and the collection counter never resets - whatever you bank in stage 1 carries forward into stage 2 and onward. There's no progress lost between sessions either, the bar just keeps filling.

Stage 1 plays close to a vanilla 6-reel ways slot with extra stacked symbols seeded into the reel sets. Stage 2 introduces Countdown Wilds - wilds with a number from 1 to 4 above them showing how many wins they participate in before being destroyed. Stage 3 enables Sure Win, which rerolls dead spins into wins with some probability. Stage 4 unlocks Respins triggered by a special Respin Wild landing inside a winning combination, with a multiplier that starts at 1x and adds +1 every successive respin. Stage 5 finally unlocks Free Spins with the bottom row revealing - until then it's locked behind a stone block barrier visible at the base of the grid. Land 4, 5 or 6 scatters during stage 5 for 8, 10 or 15 spins; multiplier ladder runs x2 to x6, and any Respin during the bonus contributes its multiplier to that ladder plus three extra spins.

Visually it sits inside a stone arch carved into a Southwest mesa, with a buffalo skull pinned to the left pillar and another to the right. The desert outside is all warm orange rock and dusty teal sky. Symbol set leans on actual painted wildlife - white horned buffalo, sharp-eyed eagle, blue-maned horse, fox with a frontier collar, green snake - and royals in red, purple, pink and blue with stripes that mimic woven cloth. Buffalo theme gets a more reverent treatment than most slots that pile on the same animal. Buy Free Spins runs at 60x bet for guaranteed entry, but you'd want at least one stage cleared first or the bonus runs without most of its features unlocked. Ante Bet at 1.5x cost is the alternative for boosting trigger frequency.