It's pretty nice but you should put the instructions or something because i lose like 10 times and i had no idea why

A few suggestions:
-> add some royalty free background music;
-> add some sound effects (when popping a circle, when losing the game, when starting and retrying a game)
-> wrap the player's sprite to the opposite side of the screen when exiting the screen's boundaries (at the moment, the player can basically exit the play area and keep going until a circle reaches the top);
-> center the score and highscore at the end (and change that font or try drawing it yourself);
-> try adding some graphics or just randomize the color of the circles that appear (and the background color when retrying);
-> add some special circles that maybe increase your speed/size (or a special circle that decreases the speed of the circles for a set time);
-> keep on improving :)

I don't seem to understand as to why do i keep losing, the number of bubbles popped is in the display but there is no time limit that must be maintained to keep popping.

So my guess is there is a time limit that keeps counting down and increases a few seconds when ever you pop a bubble and if there is no time added to to counter it gradually decreases and the game ends.

In my opinion I suggest you display that timer, if that is how this game works.
Also the Bubbles sometimes come in groups rather than in random places that is, 2 or 3 bubbles are very close to each other this results on a lot of unused area on the screen which remains blank for most of the game.

This game is pretty decent.
Well done

I liked the game it was pretty fun. the graphics while basic where pretty sharp and the hotboxes where even better but the only thing wrong with it is that there is no background music. so good on this game hope you make more.