Yes its easy to just spam space and up I agree. It was the issue with previous version. But keep in mind that the goal of the game isn't just to survive - its go get highest score possible within given timeframe! (You can brag about it among friends!)
Spamming space and up isn't the best tactic for this goal, as far as I know.
The penalty is applied when you don't use different color each time reducing combo - crucial part of high scores.
Allowing player to move in every direction would also allow to just press arrow up and go and would also introduce "missclick" issue for those who try to keep up combo
That being said we are aware of this method and I also consider it somewhat of a flaw. It would be fun excercise to come up with a solution for this problem.
Thanks for feedback!