Background: Early intervention for children diagnosed with ASD is known to be critical. However waiting lists for therapy are long; the time between diagnosis and access to formal therapy can be as much as 18 months-a delay with immense societal cost. Parents are forced to endure this delay, feeling every lost day but lacking the knowledge and tools to redeem the time. We address the needs of families marooned in waiting lists by empowering the parent with knowledge and provide early therapy in the home. Objectives: We explore the design and implementation of the iPad application TOBY Playpad, a therapist-and-parent designed early intervention program administered at home by parents. It teaches a range of skills, both on and off the iPad, within a rigorous learning framework. Methods: A team of parents and research, technical and clinical therapists collaborated over two years to design and iterate TOBY Playpad. In that time, three trials, each granting a greater degree of autonomy to the participants, have been used to evolve its design and verify its impact: The core features of the implementation are: (1) A rigorous learning framework for defining, delivering, and recording: stimuli, responses, prompting and reinforcement. (2) A multi-skill syllabus covering visual and auditory understanding, receptive and expressive language, imitation and social skills, totalling 52 skills taught in 320 tasks, completely specified in the form of a fine-grained dependency tree. (3) Algorithms for delivering the syllabus flexibly in response to each child's performance, including: Prompting levels that adapt relative to performance; Reinforcement that adapts relative to performance, at individual trial and task levels; and Measurable criteria for mastery and progression through the syllabus. (4) Natural Environment Training co-ordinated with on-iPad tasks to teach skills in the real-world, helping children to retain and generalize skills. TOBY Playpad aims to empower parents to assume the role of therapist by: supplying knowledge in the form of a comprehensive multimedia help resource; a mixed-initiative therapy planning model that gives direction while allowing for the contingencies and varying circumstances of daily life; providing rich progress reports to help guide planning choices; and programmatic support of the core aspects of ABA and DTT encoded in, e.g., mastery criteria, progression logic, and session recording; and a token-reward system that reinforces learning. Results: Three formal trials (n=8, 16, and 47; ages 2-8) have led to the following outcomes: 1.The instructional design and learning framework enabled a majority of children to learn skills over time. 2.Learning was tracked accurately, areas of difficulty were identified, and stimulus delivery was accordingly concentrated on those areas, while allowing children to move at their own pace. 3.Natural Environment Training complemented iPad-based tasks and integrated with daily life. 4.Parents expressed the sense of empowerment TOBY afforded them. Conclusions: This work delivers technology that helps parents administer a therapist-designed program at home. Through principled delivery, it is able to cover a large range of core but complex early learning skills. Critically, it fills the gap when crucial intervention time would otherwise be wasted.