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+---
+epic: 6
+story: 6.6
+title: "Conditionals"
+status: draft
+---
+
+## Epic 6 — Advanced Math & Functions
+**Goal:** Scientific, financial, and power-user math.
+
+### Story 6.6: Conditionals
+
+As a **CalcPad user**,
+I want to write conditional expressions using `if/then/else`,
+So that I can model decision logic such as tax brackets and tiered pricing directly in my calculations.
+
+**Acceptance Criteria:**
+
+**Given** a variable `revenue = 150000`
+**When** the user writes `if revenue > 100k then revenue * 0.15 else revenue * 0.10`
+**Then** the result is `22500` (the `then` branch is taken because 150000 > 100000)
+
+**Given** a variable `revenue = 80000`
+**When** the user writes `if revenue > 100k then revenue * 0.15 else revenue * 0.10`
+**Then** the result is `8000` (the `else` branch is taken because 80000 is not > 100000)
+
+**Given** the user writes `if 5 > 3 then 10 else 20`
+**When** the engine evaluates
+**Then** the result is `10`
+
+**Given** the user writes `if 2 > 3 then 10 else 20`
+**When** the engine evaluates
+**Then** the result is `20`
+
+**Given** the user writes `if x > 10 then x * 2 else x` where `x` is undefined
+**When** the engine evaluates
+**Then** an error is displayed indicating that `x` is not defined
+
+**Given** the user writes a conditional comparing values with units, e.g., `if distance > 100 km then 50 else 30`
+**When** the engine evaluates with `distance = 150 km`
+**Then** the result is `50` (the comparison respects unit context)
+
+**Given** the user writes a conditional without an `else` clause, e.g., `if revenue > 100k then revenue * 0.15`
+**When** the engine evaluates with `revenue = 80000`
+**Then** the result is `0` or `null`/blank (a sensible default when the condition is false and no else is provided)
+
+**Given** the user writes a nested conditional: `if a > 10 then if a > 20 then 3 else 2 else 1`
+**When** the engine evaluates with `a = 25`
+**Then** the result is `3`