Thanks for all the lovely feedback <3
Looking back I would include explanation of the towers at least, but I didn't want to have a complicated wall of text and rather wanted the game to be as self explanatory as possible, that's why we didn't end up removing the TTL number from the envelopes.
The signal strength I think would work better if we changed it to Signal Score and just not show the %, since it's just basically "try to get this number as high as you can", while also lowering time and tower count.
The towers themselves work in this manner:
Omnidirectional: No signal loss on terrain, low signal loss on distance (slow) Dish: High signal loss when overlapping terrain, no signal loss otherwise (faster) Beam: Long distance, high signal loss (fastest)
If I were to redo the tutorial, I would probably add maps, that already have prebuilt towers with drawn information next to it, explaining how they work.
The final signal loss is displayed on the destination, so you can try to move towers and rotate them around to get the best possible result.