Space slots
Space and sci-fi is the category where slots most often abandon the traditional reel layout. Aliens, robots, space stations and galactic backdrops are usually a pretext for building a board that behaves unlike a conventional machine: grids cleared by cascades, symbols merging into larger shapes, chain reactions. It is one of the most mechanically distinctive groups in our whole library.
Where to play for real money
If you've tried a game in demo mode and want to play for real money, here are 22 casinos that carry the slots covered on this page, with their current welcome bonuses and codes.
Advertising disclosure. The links below are affiliate links — we may be paid a commission if you open an account, at no extra cost to you. It doesn't change the RTP or the specs we publish, which come from the game provider.
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18+ only. Gambling with real money involves risk — never stake more than you can afford to lose. Terms apply at every operator and can change without notice; always read the current terms on the operator's own site. Free, confidential help: BeGambleAware.org.
9 games in this category — each one playable free in demo mode, averaging 96.13% RTP.
Studios in this category
Every game in this category
Why space means unusual boards
Because there is no template a game has to conform to. An Egyptian slot gets compared to Book of Dead, a fruit slot to a mechanical machine, a sports slot to the shape of a competition. Science fiction has no such reference point — alien organisms can look like any shape at all and behave by any rules. For a designer that is an invitation to abandon reels entirely.
So grids dominate this category: a board a few by a few, pays for clusters of adjacent symbols, symbols vanishing and refilling from above, and often several symbols merging into one larger one that covers a block of positions and pays more. That is a solution entirely foreign to the classic slot and completely natural here.
What to expect from this category
Play in which a single spin can take much longer than in a typical slot. A chain reaction — win, clear, refill, another win — can run through many steps, and with it a multiplier rises or a special-feature meter fills. The tension is therefore built inside a spin rather than between spins.
The consequence is a wide payout distribution. Most spins end after one step and give nothing, but the few where a reaction gathers pace can pay a great deal. The great majority of titles in this category are high variance, and that is a direct consequence of the mechanic rather than a separate design decision.
Typical mechanics
Cluster pays with no lines, cascades and chain reactions, symbols merging into larger blocks, multipliers rising with each step of a reaction, meters filled by hits, and features that transform the board once a spin ends. A few titles use a board that grows mid-round.
What is characteristic of the group is a multi-level structure: the first meter unlocks a feature, that leads to the next, and the last is the rarest and highest-paying event in the game. Published RTP covers that whole structure together, so there is no way to play only its most favourable part.
What to watch out for
How many symbols are needed for the lowest win and how big the board is. Those two figures together tell you more about hit frequency than the volatility label does. A large grid with a high threshold means long runs without a payout broken by single large spins.
Second: several entries in this category have RTP clearly below the typical level in our library. With mechanically unusual games it is especially easy to miss, because there is no obvious reference point — which is why we list the studio's published figure for every title.
Space and the other grid categories
If you enjoy how a space slot plays, it is not the theme you enjoyed but the grid mechanic. The same construction drives the gems category, the sweets category and part of fantasy. That knowledge is practical: instead of browsing more alien games, you'll find something you like faster by moving to a category with the same maths.
Science fiction differs from them in one respect: it uses symbol merging and multi-level special features more often. These are the most mechanically dense games in the library and they need a few dozen spins before you even understand what is happening on the board. Demo mode is close to necessary here, not merely convenient.
Space titles worth checking
Play'n GO's Reactoonz is the most recognisable entry and a good starting point: a grid with chain reactions, symbol merging and several levels of special features. Energoonz, Gigantoonz and Dr Toonz belong to the same family and show how the studio developed the idea over the years.
Contact and Planet Fortune represent a more conventional take on science fiction, Sparky and Shortz heads towards robots and meters, and Space Race has the lowest RTP in the group — worth checking in the data before you play. BGaming's Alien Fruits combines space with a classic fruit machine and also appears in the fruit category.
Other themes
18+ only. Demo games use play-money credits with no cash value. Themes are assigned by hand from each game's setting. RTP is the studio's published figure and an individual casino may run a different configuration. Play responsibly: BeGambleAware.org.