Another Ada project I am still perfecting, was my first attempt at driving OpenGL directly from Ada. Originally using SDL2, but later settling on GLFW windows and OpenAL sound:
...is a 3D slider puzzle that looks like a rubic's-cube. A 3x3x3 arrangement of cubelets with the center one missing allows sliding permutations. After a randomization, the goal is to restore the cube to its original configuration based on color and alphabetic hints. It also includes a 2x2x2 version called Seven. In either one, you can click on any cubelet adjacent to a space to move it into that space.
They too can run on Windows, OSX & Linux.