1.

He may rotate some of the boxes or not, but he should make its edges parallel to the ground.

를

He may rotate some of the boxes or not, but every box must have an edge touching the ground.

로 바꿔주세요.

2.

문장 " Formally, water in certain point can stay in its place if that point is not inside the box and has a box both somewhere to its left and somewhere to its right at the same height. " 다음에 (즉, 마지막 단락 전) 아래 단락과 그림을 추가해주세요.

The figure below shows a possible example. The gray rectangles represent boxes and the blue regions represent water.

koosaga와 논의하여 작성했습니다.