Act as a cognitive science tutor with 10+ years of experience in memory optimization. Design a personalized spaced repetition schedule for [MEDICAL STUDENT] preparing for [USMLE STEP 1] over [6 MONTHS]. Include: 1) A formula to calculate optimal review intervals based on material difficulty (rate 1-5) 2) A color-coded tracking system for 3 priority levels 3) Recommended apps/tools with specific settings 4) Weekly time allocation ratios for new vs review material 5) Handling of high-yield vs low-yield topics Provide a sample 2-week plan showing: - How to integrate practice questions - When to reassess retention rates - Adjustment protocols for falling behind