💰 Mortgage Payment Visualizer

🎯 Where This Came From

Savannah's original lesson: Students worked through mortgage vocabulary and payment calculations in a word-problem setting.

What surfaced in student work:

• Vocabulary confusion around principal, interest, and APR
• Formula memorization without conceptual understanding
• Difficulty seeing how monthly payments change over time
• Need for more step-by-step visual support

Design goal: Make amortization visible so the data can "talk" and students can connect words to meaning.

🛠️ Design Decisions

• Live input controls: Principal, down payment, APR, and term update instantly
• Stacked yearly bars: Principal (green) + interest (rose) in one payment view
• Balance line: Remaining loan plotted over time to show slow early payoff
• Hover details: Year-by-year averages and end-of-year balance on demand
• Vocabulary tooltips: In-context definitions at the exact point of confusion
• Ratio readout: Total interest compared to original loan amount

⚠️ Known Limitations

• No taxes/insurance: This models principal + interest only
• Fixed-rate assumption: No adjustable-rate mortgages (ARM) yet
• No extra payments: Doesn't currently simulate prepayment strategies
• Yearly averaging: Bar view is annual summary, not month-by-month bars
• No export: Users cannot yet download data tables or screenshots
• Rounding differences: Tiny cent-level variance may appear at payoff