Add mixed denominator fractions worksheet option

apps/web/src/app/create/worksheets/components/config-panel/OperatorIcon.tsx

@@ -1,7 +1,7 @@
 import { css } from '@styled/css'
 
 export interface OperatorIconProps {
-  operator: 'addition' | 'subtraction' | 'mixed'
+  operator: 'addition' | 'subtraction' | 'mixed' | 'fractions'
   size?: 'sm' | 'md' | 'lg' | 'xl'
   isDark?: boolean
   color?: 'gray' | 'green'
@@ -15,7 +15,8 @@ const sizeMap = {
   xl: 'xl',
 } as const
 
-function getOperatorSymbol(operator: 'addition' | 'subtraction' | 'mixed'): string {
+function getOperatorSymbol(operator: 'addition' | 'subtraction' | 'mixed' | 'fractions'): string {
+  if (operator === 'fractions') return '⅟'
   if (operator === 'mixed') return '±'
   if (operator === 'subtraction') return '−'
   return '+'

apps/web/src/app/create/worksheets/components/config-panel/OperatorSection.tsx

@@ -2,8 +2,8 @@ import { css } from '@styled/css'
 import { OperatorIcon } from './OperatorIcon'
 
 export interface OperatorSectionProps {
-  operator: 'addition' | 'subtraction' | 'mixed' | undefined
+  operator: 'addition' | 'subtraction' | 'mixed' | 'fractions' | undefined
-  onChange: (operator: 'addition' | 'subtraction' | 'mixed') => void
+  onChange: (operator: 'addition' | 'subtraction' | 'mixed' | 'fractions') => void
   isDark?: boolean
 }
 
@@ -11,6 +11,7 @@ export function OperatorSection({ operator, onChange, isDark = false }: Operator
   // Derive checkbox states from operator value
   const additionChecked = operator === 'addition' || operator === 'mixed' || !operator
   const subtractionChecked = operator === 'subtraction' || operator === 'mixed'
+  const fractionsChecked = operator === 'fractions'
 
   const handleAdditionChange = (checked: boolean) => {
     if (!checked && !subtractionChecked) {
@@ -40,6 +41,10 @@ export function OperatorSection({ operator, onChange, isDark = false }: Operator
     }
   }
 
+  const handleFractionsSelect = () => {
+    onChange('fractions')
+  }
+
   return (
     <div data-section="operator-selection">
       <label
@@ -187,6 +192,85 @@ export function OperatorSection({ operator, onChange, isDark = false }: Operator
             </span>
           </div>
         </label>
+
+        {/* Mixed-Denominator Fractions */}
+        <label
+          data-action="toggle-fractions"
+          className={css({
+            display: 'flex',
+            alignItems: 'center',
+            gap: '3',
+            cursor: 'pointer',
+            px: '3',
+            py: '2.5',
+            rounded: 'lg',
+            border: '2px solid',
+            transition: 'all 0.2s',
+            bg: fractionsChecked
+              ? isDark
+                ? 'brand.900'
+                : 'brand.50'
+              : isDark
+                ? 'gray.700'
+                : 'white',
+            borderColor: fractionsChecked ? 'brand.500' : isDark ? 'gray.600' : 'gray.300',
+            _hover: {
+              borderColor: 'brand.400',
+            },
+          })}
+        >
+          <input
+            type="radio"
+            checked={fractionsChecked}
+            onChange={handleFractionsSelect}
+            className={css({
+              width: '5',
+              height: '5',
+              cursor: 'pointer',
+              accentColor: 'brand.600',
+              flexShrink: 0,
+            })}
+          />
+          <div
+            className={css({
+              display: 'flex',
+              alignItems: 'center',
+              gap: '2',
+              flex: 1,
+              minWidth: 0,
+            })}
+          >
+            <OperatorIcon operator="fractions" isDark={isDark} />
+            <div
+              className={css({
+                display: 'flex',
+                flexDirection: 'column',
+                gap: '0.5',
+                color: isDark ? 'gray.200' : 'gray.700',
+              })}
+            >
+              <span
+                className={css({
+                  fontSize: 'sm',
+                  fontWeight: 'semibold',
+                  '@media (max-width: 200px)': {
+                    fontSize: 'xs',
+                  },
+                })}
+              >
+                Mixed Denominator Fractions
+              </span>
+              <span
+                className={css({
+                  fontSize: 'xs',
+                  color: isDark ? 'gray.400' : 'gray.600',
+                })}
+              >
+                Build fluency adding unlike denominators.
+              </span>
+            </div>
+          </div>
+        </label>
       </div>
 
       <p
@@ -196,11 +280,13 @@ export function OperatorSection({ operator, onChange, isDark = false }: Operator
           lineHeight: '1.5',
         })}
       >
-        {additionChecked && subtractionChecked
+        {fractionsChecked
-          ? 'Problems will randomly use addition or subtraction'
+          ? 'All problems will be mixed-denominator fraction addition'
-          : subtractionChecked
+          : additionChecked && subtractionChecked
-            ? 'All problems will be subtraction'
+            ? 'Problems will randomly use addition or subtraction'
-            : 'All problems will be addition'}
+            : subtractionChecked
+              ? 'All problems will be subtraction'
+              : 'All problems will be addition'}
       </p>
     </div>
   )

apps/web/src/app/create/worksheets/components/config-sidebar/TabNavigation.tsx

@@ -9,7 +9,7 @@ import { ProblemPreview } from './ProblemPreview'
 export interface Tab {
   id: string
   label: string
-  icon: string | ((operator?: 'addition' | 'subtraction' | 'mixed') => string) | 'preview'
+  icon: string | ((operator?: 'addition' | 'subtraction' | 'mixed' | 'fractions') => string) | 'preview'
   subtitle?: (props: {
     mode?: 'custom' | 'manual' | 'mastery'
     difficultyProfile?: string
@@ -29,6 +29,7 @@ export const TABS: Tab[] = [
     id: 'operator',
     label: 'Operator',
     icon: (operator) => {
+      if (operator === 'fractions') return '⅟'
       if (operator === 'mixed') return '±'
       if (operator === 'subtraction') return '−'
       return '+'
@@ -115,7 +116,7 @@ export const TABS: Tab[] = [
 interface TabNavigationProps {
   activeTab: string
   onChange: (tabId: string) => void
-  operator?: 'addition' | 'subtraction' | 'mixed'
+  operator?: 'addition' | 'subtraction' | 'mixed' | 'fractions'
   mode?: 'custom' | 'manual' | 'mastery'
   difficultyProfile?: string
   interpolate?: boolean

apps/web/src/app/create/worksheets/config-schemas.ts

@@ -342,8 +342,8 @@ const additionConfigV4BaseSchema = z.object({
       message: 'min must be less than or equal to max',
     }),
 
-  // V4: Operator selection (addition, subtraction, or mixed)
+  // V4: Operator selection (addition, subtraction, mixed, or fractions)
-  operator: z.enum(['addition', 'subtraction', 'mixed']).default('addition'),
+  operator: z.enum(['addition', 'subtraction', 'mixed', 'fractions']).default('addition'),
 
   // Regrouping probabilities (shared between modes)
   pAnyStart: z.number().min(0).max(1),

apps/web/src/app/create/worksheets/generatePreview.ts

@@ -3,7 +3,9 @@
 import { execSync } from 'child_process'
 import type { WorksheetFormState } from '@/app/create/worksheets/types'
 import {
+  createPRNG,
   generateMasteryMixedProblems,
+  generateFractionProblems,
   generateMixedProblems,
   generateProblems,
   generateSubtractionProblems,
@@ -13,6 +15,48 @@ import { generateTypstSource } from './typstGenerator'
 import { validateProblemSpace } from './utils/validateProblemSpace'
 import { validateWorksheetConfig } from './validation'
 
+function renderFractionPageSvg(
+  pageProblems: ReturnType<typeof generateFractionProblems>,
+  config: WorksheetFormState,
+  pageIndex: number
+): string {
+  const width = config.orientation === 'portrait' ? 850 : 1100
+  const height = config.orientation === 'portrait' ? 1100 : 850
+  const margin = 48
+  const cols = config.cols ?? 4
+  const rows = Math.max(1, Math.ceil(pageProblems.length / cols))
+
+  const cellWidth = (width - margin * 2) / cols
+  const cellHeight = (height - margin * 2) / rows
+
+  const problemTexts = pageProblems
+    .map((problem, index) => {
+      const col = index % cols
+      const row = Math.floor(index / cols)
+      const x = margin + col * cellWidth + cellWidth / 2
+      const y = margin + row * cellHeight + cellHeight / 2
+
+      const label = problem
+        ? `${problem.numerator1}/${problem.denominator1} + ${problem.numerator2}/${problem.denominator2} =`
+        : ''
+
+      return `<g transform="translate(${x}, ${y})">
+        <text text-anchor="middle" dominant-baseline="middle" font-size="22" font-family="Inter, Arial" fill="#111827">${
+          (pageIndex * (config.problemsPerPage ?? 20)) + index + 1
+        }.) ${label}</text>
+      </g>`
+    })
+    .join('\n')
+
+  return `<svg xmlns="http://www.w3.org/2000/svg" width="${width}" height="${height}" viewBox="0 0 ${width} ${height}">
+    <rect x="0" y="0" width="${width}" height="${height}" fill="white"/>
+    <text x="${margin}" y="${margin - 16}" font-size="18" font-family="Inter, Arial" fill="#374151">
+      ${config.name || 'Fraction Practice'} • Page ${pageIndex + 1}
+    </text>
+    ${problemTexts}
+  </svg>`
+}
+
 export interface PreviewResult {
   success: boolean
   pages?: string[]
@@ -64,13 +108,16 @@ export async function generateWorksheetPreview(
 
     // Validate problem space for duplicate risk
     const operator = validatedConfig.operator ?? 'addition'
-    const spaceValidation = validateProblemSpace(
+    const spaceValidation =
-      validatedConfig.problemsPerPage,
+      operator === 'fractions'
-      validatedConfig.pages,
+        ? { warnings: [] }
-      validatedConfig.digitRange,
+        : validateProblemSpace(
-      validatedConfig.pAnyStart,
+            validatedConfig.problemsPerPage,
-      operator
+            validatedConfig.pages,
-    )
+            validatedConfig.digitRange,
+            validatedConfig.pAnyStart,
+            operator
+          )
 
     if (spaceValidation.warnings.length > 0) {
       console.log('[PREVIEW] Problem space warnings:', spaceValidation.warnings)
@@ -78,6 +125,7 @@ export async function generateWorksheetPreview(
 
     // Generate all problems for full preview based on operator
     const mode = config.mode ?? 'custom'
+    const rand = createPRNG(validatedConfig.seed ?? Date.now() % 2147483647)
 
     console.log(
       `[PREVIEW] Step 2: Generating ${validatedConfig.total} problems (mode: ${mode}, operator: ${operator})...`
@@ -146,18 +194,52 @@ export async function generateWorksheetPreview(
                 validatedConfig.interpolate,
                 validatedConfig.seed
               )
-            : generateMixedProblems(
+            : operator === 'fractions'
-                validatedConfig.total,
+              ? generateFractionProblems(validatedConfig.total, rand)
-                validatedConfig.digitRange,
+              : generateMixedProblems(
-                validatedConfig.pAnyStart,
+                  validatedConfig.total,
-                validatedConfig.pAllStart,
+                  validatedConfig.digitRange,
-                validatedConfig.interpolate,
+                  validatedConfig.pAnyStart,
-                validatedConfig.seed
+                  validatedConfig.pAllStart,
-              )
+                  validatedConfig.interpolate,
+                  validatedConfig.seed
+                )
     }
 
     console.log(`[PREVIEW] Step 2: ✓ Generated ${problems.length} problems`)
 
+    if (operator === 'fractions') {
+      const problemsPerPage = validatedConfig.problemsPerPage ?? 20
+      const totalPages = Math.ceil(problems.length / problemsPerPage)
+      const start = startPage !== undefined ? Math.max(0, startPage) : 0
+      const end = endPage !== undefined ? Math.min(endPage, totalPages - 1) : totalPages - 1
+
+      if (start > end || start >= totalPages) {
+        return {
+          success: false,
+          error: `Invalid page range: start=${start}, end=${end}, totalPages=${totalPages}`,
+        }
+      }
+
+      const pages: string[] = []
+      for (let i = start; i <= end; i++) {
+        const startIndex = i * problemsPerPage
+        const pageProblems = problems.slice(startIndex, startIndex + problemsPerPage) as ReturnType<
+          typeof generateFractionProblems
+        >
+        pages.push(renderFractionPageSvg(pageProblems, validatedConfig, i))
+      }
+
+      return {
+        success: true,
+        pages,
+        totalPages,
+        startPage: start,
+        endPage: end,
+        warnings: spaceValidation.warnings.length > 0 ? spaceValidation.warnings : undefined,
+      }
+    }
+
     // Generate Typst sources (one per page)
     // Use placeholder URL for QR code in preview (actual URL will be generated when PDF is created)
     const previewShareUrl = validatedConfig.includeQRCode
@@ -280,6 +362,7 @@ export async function generateSinglePage(
     // This is unavoidable because problems are distributed across pages
     const operator = validatedConfig.operator ?? 'addition'
     const mode = config.mode ?? 'custom'
+    const rand = createPRNG(validatedConfig.seed ?? Date.now() % 2147483647)
 
     let problems
 
@@ -328,6 +411,8 @@ export async function generateSinglePage(
         validatedConfig.interpolate,
         validatedConfig.seed
       )
+    } else if (operator === 'fractions') {
+      problems = generateFractionProblems(validatedConfig.total, rand)
     } else if (operator === 'subtraction') {
       problems = generateSubtractionProblems(
         validatedConfig.total,
@@ -349,6 +434,20 @@ export async function generateSinglePage(
       )
     }
 
+    if (operator === 'fractions') {
+      const problemsPerPage = validatedConfig.problemsPerPage ?? 20
+      const startIndex = pageNumber * problemsPerPage
+      const pageProblems = problems.slice(startIndex, startIndex + problemsPerPage) as ReturnType<
+        typeof generateFractionProblems
+      >
+
+      return {
+        success: true,
+        page: renderFractionPageSvg(pageProblems, validatedConfig, pageNumber),
+        totalPages,
+      }
+    }
+
     // Generate Typst source for ALL pages (lightweight operation)
     // Use placeholder URL for QR code in preview
     const previewShareUrl = validatedConfig.includeQRCode

apps/web/src/app/create/worksheets/problemGenerator.ts

@@ -2,6 +2,7 @@
 
 import type {
   AdditionProblem,
+  FractionProblem,
   ProblemCategory,
   SubtractionProblem,
   WorksheetProblem,
@@ -40,6 +41,42 @@ function shuffleArray<T>(arr: T[], rand: () => number): T[] {
   return shuffled
 }
 
+/**
+ * Generate mixed-denominator fraction addition problems
+ */
+export function generateFractionProblems(
+  total: number,
+  rand: () => number
+): FractionProblem[] {
+  const problems: FractionProblem[] = []
+
+  const pickDenominator = () => randint(2, 12, rand)
+  const pickNumerator = (denominator: number) => randint(1, denominator - 1, rand)
+
+  while (problems.length < total) {
+    const denominator1 = pickDenominator()
+    let denominator2 = pickDenominator()
+
+    // Ensure denominators are different to enforce mixed denominators
+    if (denominator2 === denominator1) {
+      denominator2 = ((denominator2 + 1 - 2) % 11) + 2 // rotate within 2-12
+    }
+
+    const numerator1 = pickNumerator(denominator1)
+    const numerator2 = pickNumerator(denominator2)
+
+    problems.push({
+      numerator1,
+      denominator1,
+      numerator2,
+      denominator2,
+      operator: 'fraction',
+    })
+  }
+
+  return problems
+}
+
 /**
  * Generate random integer between min and max (inclusive)
  */

apps/web/src/app/create/worksheets/types.ts

@@ -116,7 +116,7 @@ export type WorksheetFormState = Partial<Omit<AdditionConfigV4Custom, 'version'>
 /**
  * Worksheet operator type
  */
-export type WorksheetOperator = 'addition' | 'subtraction' | 'mixed'
+export type WorksheetOperator = 'addition' | 'subtraction' | 'mixed' | 'fractions'
 
 /**
  * A single addition problem
@@ -136,10 +136,21 @@ export interface SubtractionProblem {
   operator: 'sub'
 }
 
+/**
+ * A single fraction addition problem with different denominators
+ */
+export interface FractionProblem {
+  numerator1: number
+  denominator1: number
+  numerator2: number
+  denominator2: number
+  operator: 'fraction'
+}
+
 /**
  * Unified problem type (addition or subtraction)
  */
-export type WorksheetProblem = AdditionProblem | SubtractionProblem
+export type WorksheetProblem = AdditionProblem | SubtractionProblem | FractionProblem
 
 /**
  * Validation result

apps/web/src/app/create/worksheets/validation.ts

@@ -165,10 +165,10 @@ export function validateWorksheetConfig(formState: WorksheetFormState): Validati
     errors.push('Digit range min cannot be greater than max')
   }
 
-  // V4: Validate operator (addition, subtraction, or mixed)
+  // V4: Validate operator (addition, subtraction, mixed, or fractions)
   const operator = formState.operator ?? 'addition'
-  if (!['addition', 'subtraction', 'mixed'].includes(operator)) {
+  if (!['addition', 'subtraction', 'mixed', 'fractions'].includes(operator)) {
-    errors.push('Operator must be "addition", "subtraction", or "mixed"')
+    errors.push('Operator must be "addition", "subtraction", "mixed", or "fractions"')
   }
 
   // Validate seed (must be positive integer)