Yes, once you beat a chapter, go to the main menu then click new game and select the chapter.
The # of levels in portal is not an exact number. there are the 20 main chambers 00-19, then there 3 or 4 escape levels, then a boss. It's a pretty short game but has lots of replay value.
you can only replay levels with cheats
There are 12 chapters.________ levels
Ok Portal still alive is bonus levels and there is a game called portal 2 already
You can replay levels on Assassin's Creed 2 by pressing start and going under DNA sequence.
By beating the co-op levels
Portal is the original game in the series. Portal: Still Alive is just extra levels added to the game.
You can't.
It depends on your preference. Black Ops is a shooter game that has a very popular multiplayer mode online. Portal 2 is a puzzle game that is also very successful, but personally, I don't find it to have too much replay value.
Portal or Portal 2 mods on Steam is installed by first Downloading it and extracting it. Then copy the map file into your Portal 2 maps folder which is Run the game.
Yes and Portal 2.
No, Portal is for PC only. Portal 2 is for PS3,Xbox 360,and PC. Plus it would suck on PSP.