Clever plot, more humor, new characters, and new gameplay features make the game a little better than its predecessor.
Portal 2 introduces you to a new A.I. named Wheatley. Wheatley looks like a metal basketball and speaks with a British accent. He is humorous and will help you escape from GLADOS. Thus, unlike the first game you are not alone when trying to escape the dangers of GLADOS and Aperture Science. The puzzle solving begins quite slowly as you begin to learn to solve fundamental puzzles. The learning curve is not too steep. The script for Wheatley is superbly done since he is very entertaining and constantly makes one laugh.
Eventually you will have access to the portal gun and you will be shooting portals to found your way around test chambers. Some of the puzzles are similar to those of the first game. As the game progresses the puzzles become more complex and new features are necessary to solve the puzzles in the test chambers. Flinging through portals become common so that you can reach otherwise unreachable platforms. You will have to figure out how much momentum is necessary to fling through blue and orange portals. The test chambers are quite varied: some are broken and some include malfunctioning turrets. There will be challenges that force you to figure out how to eliminate turrets using portals, gels, and excursion funnels. Gels and excursion funnels are very cool additions to the game. There is a type of gel that gives the extra speed necessary to reach another platform. Another type of gel allows you to jump higher than normal to reach a platform. There is also a type of gel that allows you to shoot a portal on an otherwise unportalable surface. Excursion funnels are horizontal or vertical liquid-looking pipes that you can jump into to progress through a test chamber. The cubes are more diverse now because there is a redirection cube, a cube that allows you to redirect lasers to receptacles in order to activate platforms. There is the addition of flight plates which are fun plates used to catapult you to another platform.
GLADOS will always be aware of where you are and is quite sarcastic in her words. She is quite complex and is still recovering from being incinerated in Portal. In later levels GLADOS becomes more likeable and will pit you against the new A.I. character.
The solving of puzzles becomes more rewarding in later levels because of the increasing complexity of the puzzles. You will have to survey your surroundings very carefully in later levels. So being able to exit the test chambers becomes quite gratifying. There is replay value because of the challenges involved and the numerous achievements. However, there are no leaderboards that would increase replay value even further. There are also secret areas to explore if you feel like exploring them. They may include turrets acting like they are playing in a musical orchestra some include beans. There is a co-op mode that allows you to solve puzzles with a friend. The co-op mode provides good replay value.
The one problem with Portal 2 is the very long load times. The long load times occur when you move from one level to the next and when you are starting from a save point for the first time after loading the game. The excessively long load times are not enough to frustrate players, but it would be best to do without them.
Fans of the Portal franchise will probably like Portal 2 better than its predecessor. Portal 2 adds to the Portal franchise by providing more creative gameplay with gels, excursion funnels and flight plates.