Thanks for playing it! The info about Firefox not working is very helpful, I should really starting testing it in browsers other than Chrome!
It should only cause a game over if two planes occupy the same tile at the same(ish) time, so if they weren’t then it was a bug.
I did want to add some planes that would need to travel to a different edge of the map and also obstacles like a hot air balloon which would float through uncontrollably to make it a bit more puzzley. Having different move distances is a great idea thanks!