The SADX Expert Mode mod essentially creates tougher level layouts for Sonic Adventure. For certain characters, such as Sonic and E-102 Gamma, each level has dramatic changes to create a new overall experience and tests your ability to think very differently when completing the levels. Techniques such as back as back tracking and using your abilities to access areas not normally accessed in the original versions of levels will be useful and sometimes necessary. Also being watchful of traps, being able to handle a large number of foes, and being quick to react to a range of obstacles such as reverse dash panels and pitfalls makes this a great challenge for players. It is highly recommended to try this mode out while having the Sonic, Shadow, and Metal Sonic Gameplay Overhaul enabled. Their unique and vast number of abilities allows for a better overall and still fast paced experience. It also provides bounds of replayability as you try out the many ways to approach each level with each character with each of their game changing abilities.