how did you make this game?

This game works and the graphics are decent. With more work and polish it would be much better.

why doesn't it say game over when you run out of lives? it just resets back to 5.

It's a start...

First and foremost, don't let yourself be discouraged by reviews here; they're supposed to be critiques to help your style evolve.

The upside:
The game itself functions, which is more than many devs can say about their first attempt at a game. I've also been somewhat missing the Mario-flavored platform.

The downsides:
Controls - While they work, the controls could do well with some more polish. Foremost, the moon-gravity effect makes it artificially difficult to control, which could in itself make for a good element if a future game was built around it. For an application like this, I'd suggest cutting the jump time to one quarter of what it currently is. (Also, the game plugin isn't completely separate from the webpage. Jumping has a tendency to scroll the page.)

Presentation - I won't nit-pick about the graphics style; this is a Flash game. The problem here is that 60% of the screen is bland background, and this severely restricts both player's accuracy, and the environment's availability. This is an easy fix though; either add more platforms to fill up the screen, move the main platform/floor closer to the center of the screen, or zoom in on the character and the action.

Repetition - You did code the restart well enough to keep the game from crashing, which I have to applaud since that isn't an easy trick all the time. However, this could also benefit immensely from a little more polish; dying and restarting as it is currently was outright jarring and had me confused the first few times I failed. A short delay with a message indicating that the player failed/died would really be all it needs to work this out.

Variety - ...It just isn't here. I don't want to nit-pick on this, but enemy variety in a Mario-style platformer is crucial to keeping the player's interest. Test around with enemies that break the standard of walking around and killing you on touch, like an archer or flying unit. These little niche enemies go a whole lot further than they would seem to in theory.

Very solid start here. I see a lot of potential in your work, so please don't cave to any of the malicious feedback you might get. Keep it coming.

its a game but i can't stand it. more explosions and ninjas! even though i don't like ninjas!