Difficult puzzles, brain teasers and conundrums

Puzzles, riddles, brain teasers, conundrums, logic questions in pictures. All the logic questions here are more difficult than the average in other sections of the site. You will most likely need more time to complete them than usual. But you can look at the answers and explanations for all these logic riddles, brain teasers and conundrums. To check your answer, click on the «Answer» button located below the task. After this, the correct answer and explanations will appear. Below you can select other questions on this topic. Typically each topic has 20 questions or more. At the same time, the complexity of logical problems gradually increases. First there will be easy questions, then medium, then difficult. Try to complete tasks as quickly as possible.
Question - 18
This difficult logic riddle-conundrum features 49 square cells, inside of which there are numbers: dark and light. Light numbers are somewhat dependent on dark numbers. You need to understand this relationship and choose the correct option for the light number to replace the question mark.
Correct answer = 2.
Here, around each light-colored number there are from three to eight dark-colored numbers. A light-colored number is equal to the number of odd dark-colored numbers nearby. An odd number cannot be divided exactly by 2. Examples of odd digits: 1, 3, 5, 7, 9, 11, 13, 15, 17, ..., 99. Shown below as an example are two counts of odd digits around light digits. These central numbers are colored yellow to make them easier to understand.
-----------------------------------------------------------------------------------------------------------------------------