 Johnson stated that Valve 's aim was not to make Portal 2 more difficult than its predecessor , but instead to produce " a game where you think your way through particular parts of the level , and feel really smart when you solve it . " Portal 2 allows the player to take incremental steps to understand the game 's mechanics , an approach that led to two basic types of test chamber . The first type , which Valve calls " <unk> " , provides a relatively safe environment for player to experiment with a new gameplay concept ; the second type combines elements in new ways to force the player to think laterally , providing challenging and rewarding puzzles . Chambers were first developed through whiteboard via isometric drawings . The developers performed a sanity check on the chamber before crafting simple levels with a software tool called the Hammer level editor . Extensive playtesting ensured the solutions to each chamber were neither too obvious nor too difficult , and observed alternative solutions discovered by playtesters . Based on play @-@ testing results , the design team retained these alternative solutions or blocked them if they were considered too easy . These versions were sent back for further play @-@ testing to verify that the new elements did not prevent players from finding solutions ; further iterations between artists and playtesters occurred until such issues were resolved . Some elements from Portal were modified to suit Portal 2 ; whereas players of Portal would be familiar with the game mechanics , novice players required some training , as would players of Portal for some game elements . For example , the energy spheres used in the first game were replaced with lasers , which provided immediate feedback and reduced the in @-@ game training time . 
