This is the fourth installment of the Fortnightly Topic Challenges Rerun described [here][1] and the thirty-seventh installment of the FTCs overall, with topics suggested and voted on [here][2]. This fortnight's topic is "***Reusing Information***" (suggested by [phenomist][5]) and will span from the **3rd of September to the 16th of September**. During this period, we will compile the list of questions with a relevant title and post it as an answer to this question. **In the meantime, please go and [propose and vote on future challenges!][2]** Everyone have fun, and happy puzzling! ----- <sub>*Link to [other][3] Fortnightly Topic Challenges.*</sub> ***NOTE*** The Reusing Information topic challenge does not have a single specific tag associated. **Due to the nature of this challenge, please add your own questions to the list below.** The [suggestion][4] is copied to this post for posterity. > #Reusing Information > Sometimes, I often particularly enjoy puzzles that reuse the same piece of information over and over. Essentially, it shares the elegance of a well constructed &lit, with whole text serving double-duty. Every word not only is used in entirety for the wordplay part, but the whole phrase could serve as a plausible definition too! Some more examples to follow: > * Encoding several different messages in the same piece of text, each one leading to the next by instructions. > * Neat meta structures sometimes allow for a set of answers to be used multiple times. The Mystery Hunt [has][11] [some][12] [examples][13]. > * Extraction from the same ciphertext twice, using (ideally) two different ciphers - could be overambitious, but this theme is ambitious. > * Next, [a picture that has three interpretations][14] - although, this is close to puzzle sets, so try to seamlessly integrate the pieces. > * Chimera / double [tag:grid-deduction] puzzles ([see this link][15]). Each grid can work in multiple rulesets. > * Letters arranged in a grid. Extraction can appear in multiple ways - for example, [some letters could be a word search, others from a grille][16]. > Note that simply reducing information and applying a recursive step isn't necessarily this - that would be using *newly* acquired data. Going back to square one is this theme's spirit! Then start over, with a fresh look, either by sheer inspiration or by explicit instruction. Have you noticed that this suggestion is itself a puzzle that self-illustrates this theme? [11]: http://web.mit.edu/puzzle/www/2011/puzzles/civilization/ [12]: http://web.mit.edu/puzzle/www/2013/coinheist.com/sneakers/index.html [13]: http://web.mit.edu/puzzle/www/2018/full/island/scifi.html [14]: https://puzzle.cisra.com.au/2010/4A-Martial-Law.pdf [15]: https://nbpuzzles.wordpress.com/2014/06/08/double-puzzles/ [16]: http://www.mezzacotta.net/puzzle/2016/4A_AllAstir.pdf [1]:https://puzzling.meta.stackexchange.com/questions/2841 [2]:https://puzzling.meta.stackexchange.com/questions/6339 [3]:https://puzzling.meta.stackexchange.com/search?tab=newest&q=is%3aq%20title%3a%22Fortnightly%20Topic%20Challenge%20%23 [4]:https://puzzling.meta.stackexchange.com/a/6362 [5]:https://puzzling.meta.stackexchange.com/users/37878