I have reduced the difficulty for the next version. I will be released on monday
The difficulty for the first level is now more what I'd expect. However, a speed (difficulty) slider would still be appreciated especially due to later levels. If that's unrealistic, then just consider an unlimited lives option. Alternatively, maybe a rogue-lite mechanic of some kind would work here. Right now it's too easy to get increasingly frustrated in a cycle of spawn-die 1 sec later-spawn-die-spawn-die-spawn-die.