📁 class-review
 ┣ 📂 grade 1
 ┃ ┣ 📂 (class name)
 ┃ ┃ ┗ 📝 (review README)
 ┃ ┗ 📝 (intro README)
 ┃
 ┣ 📂 grade 2
 ┃ ┣ 📂 (class name)
 ┃ ┃ ┗ 📝 (review README)
 ┃ ┗ 📝 (intro README)
 ┃
 ┣ 📂 grade 3
 ┃ ┣ 📂 (class name)
 ┃ ┃ ┗ 📝 (review README)
 ┃ ┗ 📝 (intro README)
 ┃
 ┗ 📂 grade 4
   ┣ 📂 (class name)
   ┃ ┗ 📝 (review README)
   ┗ 📝 (intro README)