6 files changed, 33 insertions, 4 deletions
diff --git a/frontend/src/styles/test.scss b/frontend/src/styles/test.scss
index 8a437be05..2d06e5bb2 100644
--- a/frontend/src/styles/test.scss
+++ b/frontend/src/styles/test.scss
@@ -1338,6 +1338,13 @@ body.fb-nospace {
   }
 }
 
+/* funbox underscore_spaces */
+body.fb-underscore-spaces {
+  #words .word {
+    margin: 0.5em 0;
+  }
+}
+
 /* funbox arrows */
 body.fb-arrows {
   #words .word {
diff --git a/frontend/src/ts/pages/settings.ts b/frontend/src/ts/pages/settings.ts
index 5b7e507d6..2f1cf76b0 100644
--- a/frontend/src/ts/pages/settings.ts
+++ b/frontend/src/ts/pages/settings.ts
@@ -612,6 +612,9 @@ async function fillSettingsPage(): Promise<void> {
         /_/g,
         " "
       )}</div>`;
+    } else if (funbox.name === "underscore_spaces") {
+      // Display as "underscore_spaces". Does not replace underscores with spaces.
+      funboxElHTML += `<div class="funbox button" data-config-value='${funbox.name}' aria-label="${funbox.description}" data-balloon-pos="up" data-balloon-length="fit">${funbox.name}</div>`;
     } else {
       funboxElHTML += `<div class="funbox button" data-config-value='${
         funbox.name
diff --git a/frontend/src/ts/test/funbox/funbox-functions.ts b/frontend/src/ts/test/funbox/funbox-functions.ts
index a0fe543d7..2cb71b303 100644
--- a/frontend/src/ts/test/funbox/funbox-functions.ts
+++ b/frontend/src/ts/test/funbox/funbox-functions.ts
@@ -26,7 +26,7 @@ export type FunboxFunctions = {
   getWord?: (wordset?: Wordset, wordIndex?: number) => string;
   punctuateWord?: (word: string) => string;
   withWords?: (words?: string[]) => Promise<Wordset>;
-  alterText?: (word: string) => string;
+  alterText?: (word: string, wordIndex: number, wordsBound: number) => string;
   applyConfig?: () => void;
   applyGlobalCSS?: () => void;
   clearGlobal?: () => void;
@@ -584,6 +584,12 @@ const list: Partial<Record<FunboxName, FunboxFunctions>> = {
       return GetText.getMorse(word);
     },
   },
+  underscore_spaces: {
+    alterText(word: string, wordIndex: number, limit: number): string {
+      if (wordIndex === limit - 1) return word; // don't add underscore to the last word
+      return word + "_";
+    },
+  },
   crt: {
     applyGlobalCSS(): void {
       const isSafari = /^((?!chrome|android).)*safari/i.test(
diff --git a/frontend/src/ts/test/words-generator.ts b/frontend/src/ts/test/words-generator.ts
index 7dabe7ef3..d2461d9ac 100644
--- a/frontend/src/ts/test/words-generator.ts
+++ b/frontend/src/ts/test/words-generator.ts
@@ -346,10 +346,14 @@ function getFunboxWord(
   return word;
 }
 
-function applyFunboxesToWord(word: string): string {
+function applyFunboxesToWord(
+  word: string,
+  wordIndex: number,
+  wordsBound: number
+): string {
   for (const fb of getActiveFunboxes()) {
     if (fb.functions?.alterText) {
-      word = fb.functions.alterText(word);
+      word = fb.functions.alterText(word, wordIndex, wordsBound);
     }
   }
   return word;
@@ -911,7 +915,7 @@ export async function getNextWord(
     }
   }
 
-  randomWord = applyFunboxesToWord(randomWord);
+  randomWord = applyFunboxesToWord(randomWord, wordIndex, wordsBound);
 
   console.debug("Word:", randomWord);
 
diff --git a/packages/funbox/src/list.ts b/packages/funbox/src/list.ts
index b1be30981..9038e3867 100644
--- a/packages/funbox/src/list.ts
+++ b/packages/funbox/src/list.ts
@@ -406,6 +406,14 @@ const list: Record<FunboxName, FunboxMetadata> = {
     frontendFunctions: ["alterText"],
     name: "instant_messaging",
   },
+  underscore_spaces: {
+    description: "Underscores_are_better.",
+    canGetPb: false,
+    difficultyLevel: 0,
+    properties: ["ignoresLanguage", "ignoresLayout", "nospace"],
+    frontendFunctions: ["alterText"],
+    name: "underscore_spaces",
+  },
   ALL_CAPS: {
     description: "WHY ARE WE SHOUTING?",
     canGetPb: false,
diff --git a/packages/funbox/src/types.ts b/packages/funbox/src/types.ts
index c410a911f..cd9e0c481 100644
--- a/packages/funbox/src/types.ts
+++ b/packages/funbox/src/types.ts
@@ -39,6 +39,7 @@ export type FunboxName =
   | "backwards"
   | "ddoouubblleedd"
   | "instant_messaging"
+  | "underscore_spaces"
   | "ALL_CAPS";
 
 export type FunboxForcedConfig = Record<string, string[] | boolean[]>;