1. Introduction of the game:
Arknights is an immersive and strategic mobile tower defense game that takes place in a post-apocalyptic world. Players take on the role of a Doctor, leading a team of operators known as Rhodes Island, to fight against a mysterious infection causing havoc across the world. With a unique blend of tactical gameplay and stunning visuals, Arknights offers an engaging and challenging experience for fans of the genre.

2. All characters and levels of the game:
Arknights boasts a diverse roster of characters, each with their own unique abilities and backstory. From powerful melee defenders to long-range snipers, players can strategically choose and deploy these operators to defend their bases against waves of enemies. The game features a multitude of levels, ranging from easy to difficult, ensuring a gradual progression in difficulty and allowing players to constantly improve and adapt their strategies.

3. What attracts users most to the game:
One of the biggest draws of Arknights is its intricate gameplay mechanics combined with its captivating storytelling. The game offers a rich and immersive narrative that unfolds through beautifully animated cutscenes and character interactions. Additionally, the extensive character customization options and the ability to build and upgrade your base further enhance the player's connection to the game.

4. Why it is popular:
Arknights has gained immense popularity due to its strategic depth, challenging gameplay, and visually stunning graphics. The game's tactical elements, requiring players to carefully manage their resources and operators' skills, provide a satisfying sense of accomplishment upon successfully completing difficult levels. Moreover, its compelling storyline and memorable characters have garnered a loyal fanbase.

5. When the game was released and how many versions are currently available:
Arknights was initially released in China on May 1, 2019. Since then, it has expanded globally, attracting players from all around the world. Currently, there are multiple versions of the game available, including the original Chinese version, an English version, as well as versions for other languages such as Japanese and Korean.

6. The most difficult part of the game:
One of the most challenging aspects of Arknights is the increasingly difficult stages, requiring players to constantly adapt and refine their strategies. As the levels progress, enemies become more formidable, forcing players to make careful decisions on which operators to deploy and how to utilize their unique abilities effectively. This difficulty spike adds a layer of excitement and keeps players engaged throughout their journey.

7. Strengths and weaknesses of the game:
Arknights excels in its immersive storyline, strategic gameplay, and visually appealing art style. The game offers a deep sense of progression through character progression, base customization, and challenging levels. However, some players may find the initial learning curve steep, requiring patience and careful planning. Additionally, while the game has a generous free-to-play model, it does offer in-app purchases which may deter some players.

8. What other games have been developed by the same developer:
Arknights is developed by Hypergryph, a renowned gaming studio known for their expertise in creating immersive and high-quality mobile games. In addition to Arknights, Hypergryph has also developed another popular mobile game called "Illusion Connect," which features a unique blend of turn-based combat and social interactions with beautifully designed characters.