1. Introduction of the game:
Hearthstone is an online digital collectible card game developed and published by Blizzard Entertainment. It offers a unique and strategic gameplay experience set in the Warcraft universe. Players engage in turn-based battles, utilizing a diverse array of cards and abilities to defeat their opponents and become the ultimate Hearthstone champion.

2. All characters and levels of the game:
In Hearthstone, players assume the role of powerful heroes from the Warcraft universe, each with their own unique abilities and playstyles. Some notable characters include Jaina Proudmoore, the powerful mage, Rexxar, the cunning hunter, and Gul'dan, the warlock with dark powers. The game features several levels, which are represented by different game modes and card sets. These levels include the Ranked ladder, Arena mode, and the Solo Adventure campaigns.

3. What attracts users most to the game:
The game's immersive gameplay and intuitive mechanics are major draws for users. Hearthstone offers a strategic depth that appeals to both casual and competitive players. The constant release of new cards, expansions, and updates ensures a dynamic and evolving experience, while the social aspects of the game, including friendly duels and a vibrant online community, contribute to its addictiveness.

4. Why it is popular:
Hearthstone's popularity can be attributed to several factors. Firstly, it offers a welcoming and accessible entry point for both card game enthusiasts and newcomers to the genre. The game's strong emphasis on skill and strategy, combined with its captivating visuals and audio, create an engaging environment for players. Additionally, Blizzard's reputation for high-quality games and consistent updates has garnered trust and loyalty from its player base.

5. When the game was released and how many versions are currently available:
Hearthstone was officially released on March 11, 2014, for Microsoft Windows and macOS. Since its inception, the game has expanded to various platforms, including mobile devices running iOS and Android systems. Currently, Hearthstone has several versions available, each introducing new card sets, mechanics, and features, ensuring the game remains fresh and exciting.

6. The most difficult part of the game:
One of the most challenging aspects of Hearthstone is mastering the intricacies of deck-building and card synergies. Crafting a powerful and cohesive deck requires careful consideration of card choices, mana curve, and synergy between the chosen hero's abilities and available cards. Adapting to the ever-changing metagame and anticipating opponents' strategies further adds to the difficulty.

7. Strengths and weaknesses of the game:
Hearthstone's strengths lie in its polished and accessible gameplay, along with its vibrant and active player community. The game's frequent updates and expansions, combined with its balanced reward system, create a satisfying progression for players. However, some may perceive the heavy reliance on luck in card draw and randomness as a weakness, as it can introduce an unpredictable element that may favor chance over skill in certain situations.

8. What other games have been developed by the same developer:
Blizzard Entertainment, the developer of Hearthstone, is renowned for its impressive portfolio of successful games. Some notable titles include World of Warcraft, Diablo, StarCraft, Overwatch, and the Warcraft series. Blizzard's extensive experience in the industry and commitment to quality have translated into a dedicated fan base that eagerly awaits each new release.