Don't worry. What you experience is quite normal in game development because there are so many great minds with cool ideas that it's very hard to find totally new concepts. For example, this link-twin is probably not the first released game of it's type either, because i remember playing such a game about 5 years ago on a flash-games site like kongregate.
In fact many, many indie-games i played in the last few years have been inspired by those small flash-games without anyone noticing. For example, you were able to play the core mechanics of Angry Birds in a browser-game at least one year before it's release. All they did was streamlining those mechanics, add cute, mass-compatible graphics and adapt it to a platform better suited to the mechanics.
And that's not a bad thing. In my opinion game development often is more about evolution rather than revolution. Even the most renowned developers like Blizzard have never created anything truly new. Warcraft was an evolution of Dune II, Diablo was a pimped Rogue/Hack-Clone (initially it was even turnbased), WoW had multiple ancestors like Everquest and Overwatch is very similar to Team Fortress (BTW: The Overwatch-producer took this comparison as a compliment, and not as blaming for being a clone).
Blizzard has mastered the art to just pick a game or genre and evolve/streamline/polish the heck out of it.
This of cause doesn't mean we should not try to find totally new concepts. But i think it helps to see the positive things when you encounter a game similar to yours:
- Very important: It's a proof of concept that your idea has potential! You are not the only one who thinks that the world needs your game.
- You can play and analyze the other game to determine features you could apply to your game to make it better. And on the other hand what your game could implement the other game may be missing.
So i suggest to not see your game as a clone just because you share some mechanics, but rather as a quest/challenge to find the one key-selling-point that distinguishes your game from the other. It can be anything: New mechanics, artstyle, story, easier controls or a new platform (currently AR and VR are quite popular).
If you just add only one thing that's different (maybe you already have) you will probably find people who are at least equally or even more interested in your game than the others. And if you don't find the secret ingredient, it's not a shame to just start the next game. I have thrown away countless prototypes and half-finished games, but i guess i learned something from every single one.
And as you experienced by yourself you always have the possibilty to reactivate old projects if you stumble upon the missing ingredient months or even years later. You can even simply finish and release your game as it is now and add any new ideas you find later to a sequel.
See it this way: Your first game is very solid and already has some fans. For comparison: My first 5 or so games have all been unfinished crap no one ever played. So you have all the right to pat yourself on your shoulder.