You start with 6 elements (no, not just 4) and proceed combining them to form new ones, in order to recreate the entire known world/universe of hundreds of elements.
The game includes 1400+ discoverable Elements, divided in 26 Realms, but grows substantially with updates and your suggestions. In fact if you have an idea for a combination or feel that two elements should react, the game provides a direct link for the suggestion.
Please note this game and its combinations were built from scratch and not copied from other games. Finding some key elements can be a (reasonable) challenge but it wouldn’t be fun otherwise. A multiple hint functionality that doesn’t spoil too much of the research process and send you on the right track is available in the ‘World Status’ page. If you are really – really – stuck please check the Blog. Feel like a combination should behave differently? Leave a comment in the blog!
The World Status Page shows the Realms and their discovered elements, also by clicking on an element tile you can see the reactions where it takes part. A scoring system is included (but completely optional, you can enjoy the game ignoring that) where you get big rewards for key elements or unlocking new realms. You can see a few ‘Target’ elements in the scoring help page and a you get a Random Target Element of the day too !
If you’re interested, you can also see information about an element by pressing on its name on the World Status page, to open its Wikipedia page.
Game is free with ad support.
Source: The Developer Website.