However, a game engine would usually be more generic, as opposed to specific. I would be reluctant to say that any computer game is also a game engine. Like a car engine, you provide the decorations (exterior and interior) and the engine drives it. I like to think of game engines in the same way. Most game engines are built such that you provide it with some code for the game logic (specific to the game you want to do), some models, sounds and images and stuff, and the engine makes all this come to life. So, in general, a game engine is just a set of tools (for programmers) that are integrated together and perform all the generic tasks that any game (within a certain category of games) would need, such that you only have to make cosmetic changes to create a new game.
The kind of things a game engine would do might include: rendering a 2D/3D environment, processing user-inputs, simulating physics, managing the game-data (models, images, sound effects, etc.), managing network play, etc. Of course, the level of genericity will change from one engine to another but most will allow quite a lot of customising.
So, of course, if you have software for one game, and it is reasonably well programmed, that you can certainly consider that the more central piece of it is a "game engine" for that very specific kind of game you did. But the design process involved in creating a game engine is quite different from that of creating one game, so don't go around saying "I designed a game engine" because that is far-fetched and would be interpreted by most as if you created something along the lines of professional computer game engines.
So, of course, if you have software for one game, and it is reasonably well programmed, that you can certainly consider that the more central piece of it is a "game engine" for that very specific kind of game you did.
My vision of the game was to create one code which will contain all options for game's work, and just include it in code while making GUI for game.
Like above. So I can use all of its options to make the game "alive".
I guess it's time to introduce you about my game, it's Lottery, I have already made one without even a piece of advanced programming in VB, but now I used OOP in C++ to create "engine", it goes nice for now.