That's a good start. Simple idea, interesting pixel art graphics, but there's still space for improvement.
At first, the controls feel a bit rough. I'd add a bit more force to the drag, so you wouldn't need to drag that much. It's a good thing you can click anywhere on the screen, or else it'd make you unable to jump whenever the angel is close to the bottom edge of the screen.
The game needs some sort of force indicator though, to inform us whether we are dragging the character or not. Either a bar in a corner somewhere, an outer glow, a directional arrow or a dotted line indicating the full trajectory. That's up to you, but in some way there should be visual difference between "now I'm dragging", "now I'm dragging A LOT" and "now I'm doing nothing".
But more importantly, wouldn't it be better if we were able to pass through clouds? Now you can get into unsolvable situations when several clouds in a row appear in a vertical line and you have to jump even though you know the bigger cloud above you will block you.
With one way platforms (since you said you're new to this: in Unity, just adding Platform Effector 2D component → One-Way should do the trick) the game would still remain challenging, but won't force you to commit suicides on a regular basis.
You would also get rid of the "sliding under clouds" bug which saved me a life a couple of times, I admit, but isn't exactly according to the laws of physics.
As for the score, I wouldn't subtract it below zero, nor deduct points for losing a life (but the latter is up to you). And since the main goal of the game is beating your high score, I'd save it somewhere here (you can create a public scoreboard with NG API, so players'll be able to compete with each other: http://www.newgrounds.io/get-started/).
Or at least keep track of your highscore in-game.
Also, a bunch of power-ups or flying birds you have to avoid or anything which diverts your attention from jumping clouds for a while never hurts. Or perhaps more detailed background, now it might seem a bit plain.
Now I noticed the text is a bit blurry (not sure why, perhaps it's scaled too much). It would also look better if your character faced the direction she's jumping. And if you jump very high right at the start of the game, you fall back off-screen and the screen doesn't focus back on you – that shouldn't happen, at least not until you safely land on your first cloud.
I hope some of my suggestions will be of use to you. Welcome to Newgrounds and good luck with this, or whatever you decide to make in the future.