# Modding mutation questions

**URL:** <https://discourse.cataclysmdda.org/t/modding-mutation-questions/16656>\
**Category:** The Toolbox\
**Tags:** mod\
**Created:** [September 18, 2018, 2:39pm UTC](https://discourse.cataclysmdda.org/t/modding-mutation-questions/16656 "2018-09-18T14:39:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Wondabarappa](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/wondabarappa/32/9565_2.png) [@Wondabarappa](https://discourse.cataclysmdda.org/u/Wondabarappa)\
**Post date:** [September 18, 2018, 2:39pm UTC](https://discourse.cataclysmdda.org/t/modding-mutation-questions/16656/1 "2018-09-18T14:39:48Z")

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I’m just starting out and have little grasp on how coding works. How does the code for mutations work? I see that some have visible stat changes but others that have clear effects in game have no details at all. for instance quills.  
“type” : “mutation”,  
“id” : “QUILLS”,  
“name” : “Quills”,  
“points” : 2,  
“visibility” : 3,  
“ugliness” : 3,  
“description” : “Your body is covered with large quills. Whenever an unarmed opponent strikes a part of your body that is not covered by clothing, they will receive significant damage.”,  
“prereqs” : [“SPINES”]  
where is the part that causes the actual damage return effect?

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**Author:** ![Zhilkin](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/zhilkin/32/3749_2.png) [@Zhilkin](https://discourse.cataclysmdda.org/u/Zhilkin)\
**Post date:** [September 18, 2018, 4:40pm UTC](https://discourse.cataclysmdda.org/t/modding-mutation-questions/16656/2 "2018-09-18T16:40:05Z")

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> <https://github.com/CleverRaven/Cataclysm-DDA/blob/8f0b634cde836ef9bd3cf8f909300df2855bfe93/src/player.cpp#L3202-L3219>