It's not all that challenging, and starts to get boring after a while.
More damning, the biggest challenge that levels have to offer is the fact that you don't know where teleporters will take you until you use them. Trial-and-error gameplay is one of the worst ways to add difficulty to a game.
I got to level 33 and still found it too easy, the difficulty increase isn't enough of a jump between levels...
I'm dissapointed for two whole reasons: To have a keyboard control and use the mouse button to continue each level and the simplicity of the game. The first one was more difficult ans yet, I enjoyed. But here the only hard level was the last one. That's very weak for a sequel of a fun game like "Gravity Duck".
Extremely easy game, and relies a little too much on cheap deaths to feign difficulty. The only times that death was really an issue was were the game had multiple sets of teleporters that are all identical, most with an instant death floor trap set up to kill you if you didn't know exactly which one you come out of. The levels were all kind of samey, and offered little for interesting environmental obstacles to give the levels a unique setting or theme.
One word. HOTKEYS. If game is fully keyboard-controlled, why should I use mouse to click continue? That's just dumb to move hand from keyboard to mouse every time level ends. At least stupid duck is respawning without further input. Mute&pause should be hotkeyed as well, that's kind of expected in recent games.