69%Strong matchFeed the Reactor
82%54682% positive reviews, Very Positive across 546 reviews·Idler · Auto Battler
—Build your atomic empire. Fuse elements, craft real compounds, trigger chain reactions, and break the periodic table wide open in an idle game where chemistry IS the strategy.
Compound Interest
SteamThe periodic table isn't decoration — it's your entire strategy layer. Every one of the 118 elements is a card you collect, deploy, and combine. Fill rows and columns for escalating bonuses. Watch your table light up element by element as you go from tapping Hydrogen to mass-producing Plutonium. If you've ever looked at the periodic table and thought "I could optimize that," this is your game.
Forget memorizing recipes. There are none. Any combination of elements whose atomic numbers sum to a valid target is a legal fusion. Two Hydrogens make Helium. Three Lithiums make Fluorine. There are thousands of valid paths — the system rewards you for finding the clever ones. Got a stockpile of Carbon? Find a way to spend it. The fusion chamber doesn't care how you get there.
Craft Water, Ethanol, Steel, TNT, Diamond — over 60 molecular compounds with real chemical formulas. Each compound carries synergy tags: [Oxide], [Organic], [Crystal], [Fuel]. Slot compounds that share tags into your loadout and the bonuses stack hard. This is where the theorycrafting lives. Your compound loadout IS your build, and the best builds will make your numbers do things you didn't think were legal.
Heavy elements above Polonium are radioactive — they generate fast, but they're on a timer. When they decay, they transform through real-world decay chains. Uranium cascades through Thorium, Radium, Radon, and more before stabilizing as Lead. Every step fires off an energy burst and leaves a usable element behind. One Uranium card is a time bomb of value.
Hit a wall? Trigger a Big Bang. Your elements and compounds reset, but you keep your research, your discovered recipes, and the Cosmic Dust you've earned — a prestige currency that buys permanent multipliers. Each cycle starts faster, pushes further, and earns exponentially more dust. The question isn't whether to prestige. It's when.
Unlock automation through the research tree — auto-click, auto-fuse, auto-synthesize, auto-compound, and eventually auto-prestige. Start each run hands-on, then lean back and let your atomic factory hum. Close the game entirely. Come back tomorrow to a Welcome Back screen full of scientific notation.
Steam data © 2026 Valve Corporation. Trademarks are property of their respective owners.
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The best games like Compound Interest are Feed the Reactor, SpaceChem, Opus Magnum, Idle Colony, and Sokobond.
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