It seems like I've run out of games to play. I like long, challenging and addicting games. BTW, Running Mac OSX here if you show me anything you ahve to download.
The cream of the crop...(you've probably played this before...but nonetheless) Desktop Tower Defense http://www.handdrawngames.com/DesktopTD/game.asp
'Internet Games' is pretty vague. You could give EVE a shot. It runs on OSX and Linux, and there's a 14-day free demo on mmorpg.com.
I'm still stuck playing the 10,000 gold level. That way you can upgrade your guns massively in the beginning. It's the stupid flying triangles that get me in the mid 60s and early 70s. I can't seem to make it past that. @Pun...try to make a maze out of the guns so that each bad guy will have to be exposed to that gun for the longest period of time possible. Make sure you upgrade your guns throughout so you can handle the bad guys toward the end.
You suck... I am completely addicted to this game now. My eyes are crossed trying to figure out how to kill those darn dark ones!!!
I play these online challenge site: http://www.hackits.de http://deathball.net/notpron/ It's pretty fun and addicting at the beginning, then it get painful and just piss you off as it goes on. But its so rewarding sometime after you make pass some challenge.
To kill the giant airplanes, arrange 6 squirt towers and two swarm towers around the dead center, and in the dead center put a boost tower. You have to upgrade the Squirts to Typhoons, the Swarms up to 310 level, and the Boost to maximum. You need a freeze tower close to each opening where they come out, that slows them down to get whacked. I use a very simple maze, just directing the first levels to middle where I start with three squirt towers ASAP (verticle just left of the dead center), then I just make them circle around the middle where I build the fortress above. Sell the Swarms as soon as the big planes are dead and buy 6 more typhoons and another boost. You'll kill everything and break 8,0000. If you know all this already, you probably need a job.
desktop tower defense is great but i actually like xeno tactic even more. this game is just so addictive.