Yeah, sounds very doable in DBPro or even DBClassic.
Besides some basic 2D commands, image pasting, sprites maybe or even 3D objects, it could work in 3D too, like top down with a terrain and little tanks that crawl over the terrain.
So that part of it can get as complex as you like - I think it'd be sensible to use PASTE IMAGE, rather than sprites or 3D for now, this is something that you could develop as your skills do. The other aspect would be some trigonometry, like working out angles and distances.
Perhaps you could make the pencil fall a more skilled thing, like have a target spin round fast, depending on the distance to the enemy, like if the enemy is really close, spin the target reasonably slowly, if it's far away spin it real fast. Then you instantly adopt a more strategic game, stay away and risk the difficult targetting, or get close to make things easier, but also easier for your enemy. DB has a atanfull command, pass the position differences to this, and it returns the angle between them - that would make it very easy to add AI and stuff.
I can imagine simply aiming at the enemy tank with the mouse with this indicator spinning round, the further away from the target, the faster the spinning gets - then when the target is lined up you press the mouse button to fire. This could develop into a really strategic game, maybe using several tanks each and letting each one move a small amount before firing - when you come to program the game, the actual difference in coding 2 or 20 tanks is very small, in fact it might be good practice to allow for lots of tanks at the outset - using arrays to store each tanks properties.
Even if you have no programming experience, you should still give it a try - there's a wealth of tutorials to get you started, really I think you'll find a lot of help for this type of project if you need it, straightforward turn-based gameplay is very easy in DB.

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