Photosensitive is an achievement that can be unlocked on the Nintendo DS and Nintendo DSiWare versions of Plants vs. Zombies. To achieve it, the player must complete a Night level without picking up any sun. Puff-shrooms are extremely mandatory to use for this achievement because they do not cost any sun.
Its name is a portmanteau of the words "photosynthesis," a process used by plants to convert light energy into chemical energy and "sensitive," meaning quick to detect or respond to slight changes, signals or influences.
This achievement is not as hard as it sounds in certain levels. On Level 2-1, just plant as many Puff-shrooms as you can (you can also use two Scaredy-shrooms if you play Level 2-1 again), and you will easily unlock it. You can also use the Garden Rake and Potato Mines, so that you can build your defense consisting of Puff-shrooms rapidly. You will be stuck with 50 sun which is worth two Potato Mines, so use them wisely. Squashes and Wall-nuts, which cost 50 sun, are not recommended for getting this achievement. Just remember to take caution of the graves, since you cannot use the Grave Buster. It is recommended that you bring along the Imitater to imitate Puff-shrooms. This way, you can plant up to ten Puff-shrooms in an extremely fast rate.
- Note: Completing a Fog level, even with Sea-shrooms, will not count towards this achievement. You also cannot earn it in Whack a Zombie, Beghouled, Beghouled Twist, The Zomboss Battle, or Vasebreaker.