Welcome to ChemHex!
In the game of ChemHex, the goal is to earn points by placing atoms and completing molecules. There are seven elements in the game: Helium(no bonds), Hydrogen(one bond), Oxygen(two bonds), Nitrogen(three bonds), Carbon(four bonds), Chemical X(five bonds), Chemical Q(six bonds), and the Mystery Element, which turns into one of the other elements when it is placed. A molecule is complete when there are no extra bonds available. For example, an Oxygen atom connected to two Hydrogen atoms makes a complete molecule, but a Nitrogen connected to those same two Hydrogen would still leave an extra bond.
You place new atoms onto the circles on the board, optionally rotating them to fit first. Atoms cannot be rotated once they are placed. Choose the position and orientation of atoms carefully, or you will paint yourself into a corner. Green circles are places where the current atom can be placed. Yellow circles are places where the current atom might be placed if it were rotated. Red circles are places where the current atom cannot be placed no matter how you rotate it. You may rotate either by dropping an atom onto a rotation button, or by pressing the left and right arrow keys on the keyboard.
Helium(He) and the Mystery Element(?) are special atoms. When a Helium is placed, it will immediately disappear, taking along with it any adjacent atoms. When the Mystery Element is placed, it will change into whatever atom will fit there, depending on how many bonds are adjacent. If there are no adjacent bonds, it will turn into a Helium, and behave just like a Helium would.
Chemical Q is also a special atom, as you are never given one during the course of a game. The only way to make Chemical Q is to use a Mystery atom on a space that connects to six bonds.
Scoring for completed molecules is 2 times the number of bonds for each atom, so 2 for each Hydrogen, 4 for each Oxygen, 6 for each Nitrogen, 8 for each Carbon, 10 for each Chemical X, and 12 for each Chemical Q. This scoring is only for completed molecules. When an atom is eliminated by the use of a Helium, it only gains 1 point per bond. Helium itself is worth absolutely nothing.
The atoms of the game are determined randomly, and start out with each element having a certain percent chance of coming up. This probability is indicated on the bottom of the screen. As molecules are completed, these probabilities change. If you make a lot of small molecules(worth less than 25 points), you will find Chemical X more common. If you make midsized molecules(worth between 25 and 100 points), Carbon will appear more often. If you make large molecules(worth at least 100), you will see more Nitrogen.
While ChemHex has a chemistry theme, it does not claim to be true to the science of chemistry. While several real world molecules can be made (like H2[molecular hydrogen], H2O[water], NH3[ammonia], CH3OH[methanol]), most molecules you make would be impossible.