Is the fourth game a good starting point in the series?

Yes, you don't need to have played the earlier temples. Crystal Temple introduces its mechanics from scratch and walks new players through them. Veterans will find the new crystal puzzles refreshing without needing prior series knowledge to enjoy.

What's the hardest level?

Difficulty is subjective, but the late-game levels combining crystal manipulation, light beam routing, and multi-stage character switching are the most demanding. Most players agree the final third significantly steps up the challenge.

Can two players use one keyboard?

Yes, this is the classic way to play cooperatively. One player on WASD, the other on arrow keys - the keyboard is wide enough that two hands have room. It's one of the most accessible local co-op games available.

Does the game save progress?

Completed levels save in your browser's local storage, and the level select makes it easy to return to specific ones. As long as you don't clear browser data, your progress is preserved across sessions.

How long does it take to finish?

Casual play through all levels takes several hours. Diamond collection completion roughly doubles that. The replay value is high because levels can be tackled cooperatively or solo for different experiences.