Hard to the point of impossible
The presentation was OK but the game started off very hard and just got harder. I'll have to take your word that there was 5 lives, I was getting rushed by so many ships on level 2 that I just couldn't get past it. Level 1 should generally be considered to be a training level in order to teach the player the skills they need for the rest of the game, then you slowly ramp up the difficulty from that point. Speaking of training, some instructions would have helped.
There wasn't enough variety in the gameplay, just moving the mouse and clicking. At the very least you could do with different shot types, ships or being able to move your ship.
Also the level endings weren't very well defined - level 1 suddenly ended while there were still ships on the screen. If you're going to end levels when the player has reached a certain time, it's a good idea to put some sort of timer on the screen. At one point during level 2 all the ships suddenly disapeared then launched from the edge of the screen again, almost as if I'd got to level 3 but without the level 3 sign.
It wasn't a bad effort, but you needed to take it much further in both concept and testing.