Just type in anywhere:

 ATLANTA    = Unlimited lives
 FARMINGTON = Turbo boost
 EUREKA     = Carry more
 BOSTON     = Win level
 CHICAGO    = All keys

 Level codes:

 Level 2  - Hyacinth
 Level 3  - Meridian
 Level 4  - Kickback
 Level 5  - Interval
 Level 6  - Yearling
 Level 7  - Ambrosia
 Level 8  - Positron
 Level 9  - Clavicle
 Level 10 - Daffodil
 Level 11 - Dictator
 Level 12 - Blackout
 Level 13 - Laburnum
 Level 14 - Zucchini
 Level 15 - Eyeglass
 Level 16 - Frippery
 Level 17 - Guardian
 Level 18 - Nuisance
 Level 19 - Ornament
 Level 20 - Mishmash