 The first two test levels created for the game did not ship in the final version for being too open and featuring too many polygons . During the summer of 1995 , the team focused on creating levels that were functional as well as fun and used the Cortex factory levels to experiment on this goal ; the mechanical setting allowed the team to forego the complex and organic forest designs and distill the two @-@ axis gameplay in an attempt to make it fun . Their first two successful levels ( " Heavy Machinery " and " Generator Room " ) utilized 2.5D gameplay and featured basic techniques previously used in Donkey Kong Country , such as steam vents , drop platforms , bouncy pads , heated pipes and enemy characters that would move back and forth , all of which would be arranged in progressively more difficult combinations as the level went on . " Willie " ' s jumping , spinning and bonking machanisms were refined in these two levels . The level " Cortex Power " incorporates the original " Sonic 's ass " point of view ( behind the character and over his shoulder ) featured in the two test levels . After working on those three levels , the first successful jungle @-@ themed level ( later titled " Jungle Rollers " ) was created from pieces of the failed first test level arranged into a corridor between trees . From that point forward , two to three levels would be created for each level theme featured , with the first level featuring an introductionary set of challenges and later levels adding new obstacles ( such as dropping and moving platforms in the second jungle @-@ themed level ) to increase the difficulty . 
