Already the ancient Greeks trained their logical thinking by solving geometric problems: Great mathematicians competed with each other.
The great advantage of geometry over other mathematical disciplines is that one can formulate the most difficult problems without assuming much in-depth knowledge.
Following this tradition I have designed the program "Treasure of Thales". A total number of well over 100 problems is available in the form of treasure hunts ranging from very elementary easy tasks to extremely difficult competitive ones. Pupils, students, moms and dads, grandmas and grandpas, simply everyone can test themselves to see how well they can keep up with the ancient Greeks.
All tasks are formulated as a treasure hunt and require a construction of the place where the treasure is believed to be hidden.
At the beginning, each treasure hunter is endowed with 100 thalers. They can be used to get some help, to dig for some treasure or to buy construction tools. The funds increase with each discovered treasure. Generally, you can solve all tasks without any restrictions. However, if you need a lot of help or if you often dig in the wrong place, you will run out of thalers.
In this case you have two options:
1. Buy additional thalers in the App Store.
2. Remove this restriction by purchasing "Unlimited" in the App Store. Hence, you can continue digging, even if you have no more thalers. Your account balance will simply become negative.
Although I have invested a lot of time in this program I still make it available for free. It should be an incentive for everyone not to need an in-app purchase.
However, by purchasing "Unlimited" you will not only appreciate my work, but you will also benefit from a multi-user environment: Multiple players using the same device or different devices (with iCloud sync) can compete against each other and compare their efforts to the high score, e.g. find out who is the best constructor in the family.
This latter option should also be interesting for schools. Using the "Unlimited-Version" schools can store the data on an external medium, e.g. a school server. The school admin will consequently be in charge of managing the data.
Finally, some last advice: Do not start immediately with the tasks of "the peak of geometry", but first collect thalers in "the valley of basic constructions". Showing some perseverance you will find there some very helpful construction tools, which you otherwise would have to acquire by spending some of your precious thalers.