Thanks for the reply!
Readability was also an issue for the blocks you couldn't land on either (ones with an X). Not sure if it was on purpose, a missing upgrade, or something I didn't understand. I just figure the X meant I couldn't stand on it, but at that point I wasn't sure why it was there.
As far as the radiation blocks go, affordances and signifiers go a long way. So if they shared color/appearance to the radiation clouds, the connection may be stronger. You could also have like a sound cue when approaching radiation like the radioactive detector static commonly found in games.