I’m trying to write a solver using Z3’s .NET library for the Towers puzzle format. Adding the constraints for “every row and column has a distinct permutation of 1-5” is simple enough, especially cribbing from the Sudoku solver provided as an example for Z3. However, I am stuck on the “Exactly X towers are visible from the left/right/top/bottom of each row/column” constraint, and specifically checking how many towers are visible from each point. It should be as simple as