I've played this game alone and also co-op. Of course the co-op version ist the most enjoyable one, because you need to rely on the other player and communicate, wich leads to funny and very challenging moments. But as single player you brain has to do the work of two players which is fun and challenging too. The map is "big", build up the difficulty slowly and has the checkpoints at the right spots.
For an 48h game jam game is this brilliant! Keep it up!!!!