Unity3D is a game development engine, which is easy to use, once you know how, and extremely powerful. Here's my first game I made in it. I may or may not add more levels and/or hazards...
Play Online: http://www.theadamgaskins.com/Unity/Platformz/
Windows Download: http://www.theadamgaskins.com/Unity/Platformz/Windows.zip
Macintosh Download: http://www.theadamgaskins.com/Unity/Platformz/Macintosh.zip
Unity allows me to export into web format, Windows standalone format, and Macintosh standalone format. The unity webplayer is required to be installed to execute the web player; I don't know about the standalone versions.
Anyways, you have three lives. If you lose them all, its gameover. On the Gameover screen, click to go back to the main menu.