Plato's prisoners are chained facing a wall and see only shadows cast by things carried behind them. Those shadows are the lowest grade of awareness — eikasia, the mere image. Taking them for reality is the cave.
A single shadow is opinion (doxa), not knowledge: many different Forms can cast the very same silhouette. A cube and a tall square prism are identical from the front, so one square shadow cannot tell them apart.
Gathering shadows that disagree — a square, then a rectangle, then a hexagon — rules the imposters out one by one. When a single Form accounts for every shadow, opinion has become knowledge (episteme): the ascent from the cave.
Some Forms are shadow-identical: no view from the wall can ever separate them. That is the cave's hard limit — you cannot judge a copy as a copy unless you already know the original.
Something in the simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.