Inclusion Criteria:
* Age at enrollment is 18 to 85
* Leg impairment from unilateral stroke at least 6 months prior to screening
* Severe to moderate gait impairment (ambulatory with a maximum walking speed of 0.8 m/s, i.e., half of normal speed)
* Able to stand without assistance
* Clinically observable gait asymmetry
* Abnormal co-activation between adductor magnus and rectus femoris (R greater than or equal to 0.5)
Exclusion Criteria:
* Cognitive impairment with at least moderately impaired attention on digit-span test, or unable to follow instructions of the MINT task
* Visual impairment (such as hemianopia) preventing sufficient perception of the screen to play the games
* Anesthesia or severe neglect in the affected leg, or visual hemineglect (score of 2 on the NIH Stroke Scale Extinction and Inattention subtest) that impairs ability to play the games
* Participation in another study on the affected leg, or any pharmacological study, within 6 weeks of enrollment
* Inability to understand or follow commands in English due to aphasia or other reason that makes it impossible to perform the training
* Diffuse or multifocal infarcts
* Substantial leg or other pain preventing participation for 60 minutes a day
* Spasticity treatment (pharmacological or Botox) on the affected leg within past 3 months
* Severe osteoporosis causing hip or other fractures
* History of multiple falls within the last year, use of walker for balance, or falling during stance while in the lab in the first session.
* Contracture limiting the range of motion of the leg
* Current pregnancy
* From the TMS portion of the study only: History of epilepsy in adulthood requiring antiseizure medications; recent/current alcoholism or benzodiazepine/barbiturate abuse or recent history of alcohol/benzodiazepine/barbiturate withdrawal, recent history of cocaine or amphetamine use, skull fractures or skull deficits, concussion within the last 6 months, unexplained recurring headaches, vagus nerve stimulator, cochlear implant, deep brain stimulator, intracranial/carotid stents, cardiac pacemaker/AICD.
