Why Solitaire’s falling cards leave a trail
In the familiar card cascade, the cards seem to stream down the screen, leaving colored, overlapping shapes behind them. The effect comes from a simple change in how the animation redraws the display: it does not clear each card’s previous position before drawing the card in its new one.
A sprite is a small graphic—here, a card image—that the program moves across the screen. In an ordinary animation, the computer erases or repaints the old location, then draws the sprite at its next position. That cleanup keeps the image looking like a single card in motion. During the cascade, the screen-wipe step is disabled, so the old pixels remain. Each new position adds another image to the trail.
A moving card becomes a stack of past frames
The computer is still moving and redrawing the card; it is the display that retains evidence of earlier positions. As successive frames accumulate, those leftover pixels form the cascade. The result turns a routine movement into a screen-filling flourish without requiring the card graphic itself to change shape.
That small rendering choice is what makes the animation memorable: the falling cards appear to multiply, while the trail is really a record of where each sprite has just been.
