[Imabi.org](https://imabi.org) is a private website with an extensive if not exhaustive review of Japanese grammar. It has detailed English explanations supported by Japanese case examples and provides deep explanations without losing focus. While it’s best for intermediate to advanced learners, it also shines in its explanation of mundane “beginner” concepts especially when there are nuances that learners neglect.
For example, [check out this breakdown of the mundane word 元気, which has nuances unbeknownst to many intermediate learners](https://imabi.org/how-to-use-%E5%85%83%E6%B0%97/).
[This article explanation of 開く (あく vs ひらく) is among the best available on the subject](https://imabi.org/intransitive-transitive-part-1/).
It’s organized by difficulty level followed a section on Classical Japanese.
I was surprised to only discover this after years of study. I hope it helps you as much as it has helped me.
by Smooth-Ask4844