Circadian Light Exposure Adjustment for Restfulness

Inclusion Criteria: * Inclusion requires that children are aged 5.0-6.9 years at the time of enrollment with a parent-reported sleep onset of ≥ 60 min after parents' desired bedtime at least three nights per week. One adult parent of each participating child will also take part in the study. Parents must be able to provide consent for themselves and their child and to complete the interview at the end of the study. Exclusion Criteria: * Children are excluded for the following reasons: * All sleep disorders as indicated on the telephone screener or by clinical cut-off scores on the Children's Sleep Habits Questionnaire (CSHQ), except for insomnia or DSWPD as features of these disorders are directly targeted by the intervention. Secondary analyses will explore if outcomes differ among participants with or without parent-reported symptoms consistent with these diagnoses. * Physical abilities that interfere with assessments (e.g., visual impairment), developmental disabilities (e.g., autism, attention-deficit/hyperactivity disorder (ADHD), pervasive developmental disorder), epilepsy or other neurological disorders, metabolic disorders, medical conditions that commonly require treatments or assessments during the night (e.g., cancer, diabetes, active asthma), current infection or lead poisoning; a head injury involving loss of consciousness in the past 6 months. * Current use of medications affecting daytime sleepiness, the circadian system, or light sensitivity. * Eye disorders or color blindness (determined with Ishihara Color Vision Test); corrected vision with eyeglasses is permitted.