In the original Plants vs. Zombies, the player can accumulate a maximum of 9,990 sun. Once that cap is reached, collecting or producing additional sun cannot raise the displayed total any further.
Sun is the game’s core resource: players spend it to plant offensive, defensive, and resource-producing plants. Sunflowers and their upgrades generate additional sun, while falling sky-suns provide another important source during daytime levels. Because most plant costs are multiples of 25, the resource system normally feels neatly rounded, making the unusual 9,990 ceiling easy to overlook.
The cap is not 9,999 or 10,000, despite both numbers being plausible guesses. It is a gameplay limit built into the original title rather than a target players are expected to reach during ordinary Adventure levels. The maximum becomes more relevant in survival, puzzle, or endurance-style play, where players may deliberately save resources between waves and build an unusually large reserve.