No one can tell you what one investment will do over 30 years — so this bench rolls the dice 200 times at once. Each faint line is one possible lifetime of the same savings plan.
Stocks earn more on average but swing hard; bonds barely beat inflation but sit still. Slide toward stocks and the fan of futures both lifts and widens — that spread is the risk, and it is the same knob as the reward, just seen twice.
The three bold rails are the 10th, 50th, and 90th percentiles: 8 in 10 futures land between the outer two. Watch the worst-tenth rail — for a long saver it can climb above what a lifetime of pure bonds would ever pay.
Real markets have wobbled roughly this much: stocks near 7% a year after inflation with big swings, safe bonds near flat. Past odds are not a promise — but the shape of the fan is real.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.