I like Calculation solitaire because skill is a major factor for winning. The game is easy to learn and may help the little ones with their arithmetic. For example: adding 4 to 11 results in 15, and subtracting 13 is 2, the next card in the 4s stack after Jack (Knave).
In Calculation, we build a foundation of four stacks to Kings counting by 1s in the first stack, 2s in the second, 3s in the third, and 4s in the last. The first stack is simply A - K. The second begins with 2 and reaches King counting by 2s. Cards may be discarded to four piles in any order with a strategy of counting backward by 2s, 3s, or 4s as to later play them in sequence to the foundation. See “How to Play Draco Calculation” for details.
For Draco Calulcation, I painted all the cards using Procreate and Photoshop with support for several languages. See “Cards Art” for samples of the face cards. The English face cards have K-Q-J face cards and French has R-D-V face cards. Depending on how your region is set on your iPhone or iPad determines which cards you see by default. Optionally, you may choose numbered face cards in Settings app. I included some fun features such as shaking the iPhone loosens up the discard piles as to see them better and a suggestion feature to help beginners with a floating hand showing where to play a card. For experts, choose Expert difficulty to reduce the discard piles to three.
Draco Calculation is now available for iPhone and iPad.