Such a cool idea for this theme. I've seen a lot of games with similar ideas, reshaped into different games. This one is totally unique so far. I upgraded the pendulum a lot first, but found that whatever benefits the diamond provided weren't outweighing the cost of not gaining as much from each swing.
I think the theme was incorporated very well, and as I said before, I haven't seen it used in this way before. I do think the gameplay could be expanded a bit, and if you plan to keep developing it, it could be really incredible. Something to divide the attention, change the rhythm, block the swing, or put the nodes in different spots would be really cool. This has a lot of potential for expansion and I hope you go with it. The art style is also perfect for this type of game and the tone that it has. The 2 colors you picked work great together. The music was fitting and kind of eerie. Overall, excellent game, this is in my top 10 for sure. Well done!