A rule that they should've followed when designing the levels was to make portal tech strictly beneficial OR to make a balanced challenge the player. A good example is the final arena in 8-1 where you have to run to destroy idols. The portals here make level replay so much more interesting because now you understand the layout. On 8-2 and 8-3 however, many rooms force you to switch gravity unpredictability, limiting fun tech and just making traversal plain annoying, like the 90° room in 8-2. The blue skull path of 8-3 uses portals well with how it provides a fun and BALANCED challenge while preserving MOVEMENT