Cuboid Volume SLS Interactive - Optimized Version

Files:
- cuboid_volume_sls_interactive.html

Update notes:
- Answer labels are now compact and kept on one line where possible.
- The visible green confirmation boxes are smaller and more transparent, so they do not block formula text such as "Volume".
- Drop areas keep a larger invisible touch/smartboard hitbox for usability while the visible label stays inside the worksheet blank.
- The activity remains fully self-contained with embedded CSS, JavaScript, and image data.

Deployment:
Upload or embed cuboid_volume_sls_interactive.html directly in SLS or an iframe.
Recommended iframe height: 450px.

Precise drop-zone update: visible drop borders are inset to match the printed worksheet rectangles while the invisible hitboxes remain larger for touch/smartboard use.
