Surprisingly my team initial goal with "only one" stayed perfectly on script.
One player making it across the battle field with no one but himself/herself (Bird courier). We added the element of one key being press to stay a float and the key would change every time you went by a sign. We thought of having multiple levels but figured only one would be best.
Everything was made from scratch and man was it fun. Have a look: https://itch.io/jam/gmtk-2019/rate/462996