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It Wasn't a Straight Line

📈 1,000 at 6% a year for 30 years. Simple interest gives 2,800; compounding gives 5,743 — same money, same rate, a 2,943 gap. Move the three sliders. For the first year the two lines sit on top of each other; after that only one of them bends upward. Simple interest pays on the principal alone, while compounding also pays on what has already grown. ✌️ Second, doubling. Pick a rate and guess the year it doubles — it's a division, not a multiplication. 6% takes 12 years, 8% takes 9. Divide 72 by the rate and you land within a year of the true answer (the Rule of 72). ⏳ Third, starting late. Same amount, same rate; the only difference is when you began. Waiting ten years costs you 2,536 after thirty. Time beats principal. This app was made with code too · Remix it with your own rate and horizon.