diff --git a/src/evaluator/evaluator.ts b/src/evaluator/evaluator.ts
index ac62ad5..b1b8664 100644
--- a/src/evaluator/evaluator.ts
+++ b/src/evaluator/evaluator.ts
@@ -1,6 +1,8 @@
 import { Tree, type SyntaxNode } from '@lezer/common'
 import * as terms from '../parser/shrimp.terms.ts'
 import { RuntimeError } from '#evaluator/runtimeError.ts'
+import { assert } from 'console'
+import { assertNever } from '#utils/utils.tsx'
 
 export const evaluate = (input: string, tree: Tree, context: Context) => {
   let result = undefined
@@ -22,8 +24,20 @@ export const evaluate = (input: string, tree: Tree, context: Context) => {
 }
 
 const evaluateNode = (node: SyntaxNode, input: string, context: Context): any => {
-  const evalNode = syntaxNodeToEvalNode(node, input, context)
+  try {
+    const evalNode = syntaxNodeToEvalNode(node, input, context)
+    return evaluateEvalNode(evalNode, input, context)
+  } catch (error) {
+    if (error instanceof RuntimeError) {
+      throw error
+    } else {
+      console.error(error)
+      throw new RuntimeError('Error evaluating node', node.from, node.to)
+    }
+  }
+}
 
+const evaluateEvalNode = (evalNode: EvalNode, input: string, context: Context): any => {
   switch (evalNode.kind) {
     case 'number':
     case 'string':
@@ -35,21 +49,20 @@ const evaluateNode = (node: SyntaxNode, input: string, context: Context): any =>
       if (context.has(name)) {
         return context.get(name)
       } else {
-        throw new RuntimeError(`Undefined variable "${name}"`, node.from, node.to)
+        throw new RuntimeError(`Undefined variable "${name}"`, evalNode.node.from, evalNode.node.to)
       }
     }
 
     case 'assignment': {
       const name = evalNode.name
-      const value = evaluateNode(evalNode.value.node, input, context)
+      const value = evaluateEvalNode(evalNode.value, input, context)
       context.set(name, value)
-
       return value
     }
 
     case 'binop': {
-      const left = evaluateNode(evalNode.left, input, context)
-      const right = evaluateNode(evalNode.right, input, context)
+      const left = evaluateEvalNode(evalNode.left, input, context)
+      const right = evaluateEvalNode(evalNode.right, input, context)
 
       if (evalNode.op === '+') {
         return left + right
@@ -60,9 +73,27 @@ const evaluateNode = (node: SyntaxNode, input: string, context: Context): any =>
       } else if (evalNode.op === '/') {
         return left / right
       } else {
-        throw new RuntimeError(`Unsupported operator "${evalNode.op}"`, node.from, node.to)
+        throw new RuntimeError(
+          `Unsupported operator "${evalNode.op}"`,
+          evalNode.node.from,
+          evalNode.node.to
+        )
       }
     }
+
+    case 'arg': {
+      // Just evaluate the arg's value
+      return evaluateEvalNode(evalNode.value, input, context)
+    }
+
+    case 'command': {
+      // TODO: Actually execute the command
+      // For now, just return undefined
+      return undefined
+    }
+
+    default:
+      assertNever(evalNode)
   }
 }
 
@@ -73,8 +104,9 @@ type EvalNode =
   | { kind: 'string'; value: string; node: SyntaxNode }
   | { kind: 'boolean'; value: boolean; node: SyntaxNode }
   | { kind: 'identifier'; name: string; node: SyntaxNode }
-  | { kind: 'binop'; op: Operators; left: SyntaxNode; right: SyntaxNode; node: SyntaxNode }
+  | { kind: 'binop'; op: Operators; left: EvalNode; right: EvalNode; node: SyntaxNode }
   | { kind: 'assignment'; name: string; value: EvalNode; node: SyntaxNode }
+  | { kind: 'arg'; name?: string; value: EvalNode; node: SyntaxNode }
   | { kind: 'command'; name: string; args: EvalNode[]; node: SyntaxNode }
 
 const syntaxNodeToEvalNode = (node: SyntaxNode, input: string, context: Context): EvalNode => {
@@ -94,78 +126,122 @@ const syntaxNodeToEvalNode = (node: SyntaxNode, input: string, context: Context)
       return { kind: 'identifier', name: value, node }
 
     case terms.BinOp: {
-      const [left, op, right] = destructure(node, ['*', '*', '*'])
+      const { left, op, right } = getBinaryParts(node)
       const opString = input.slice(op.from, op.to) as Operators
-      return { kind: 'binop', op: opString, left, right, node }
+      const leftNode = syntaxNodeToEvalNode(left, input, context)
+      const rightNode = syntaxNodeToEvalNode(right, input, context)
+      return { kind: 'binop', op: opString, left: leftNode, right: rightNode, node }
     }
 
     case terms.Assignment: {
-      const [identifier, _equals, expr] = destructure(node, [terms.Identifier, '*', '*'])
-
+      const { identifier, value: expr } = getAssignmentParts(node)
       const name = input.slice(identifier.from, identifier.to)
       const value = syntaxNodeToEvalNode(expr, input, context)
-
       return { kind: 'assignment', name, value, node }
     }
 
     case terms.ParenExpr: {
-      const [_leftParen, expr, _rightParen] = destructure(node, ['*', '*', '*'])
+      const expr = getParenParts(node)
       return syntaxNodeToEvalNode(expr, input, context)
     }
 
     case terms.CommandCall: {
-      const [_at, identifier, _leftParen, ...rest] = destructure(node, [
-        '*',
-        terms.Identifier,
-        '*',
-        '*',
-      ])
+      const { commandName, argNodes } = extractCommand(node, input)
+
+      const args = argNodes.map((argNode) => {
+        const children = getAllChildren(argNode)
+
+        if (argNode.type.id === terms.Arg) {
+          const [child] = children
+          if (!child) {
+            throw new Error(`Parser bug: Arg node has ${children.length} children, expected 1`)
+          }
+          const value = syntaxNodeToEvalNode(child, input, context)
+          return { kind: 'arg', value, node: argNode } as const
+        }
+
+        if (argNode.type.id === terms.NamedArg) {
+          const [nameChild, valueChild] = children
+          if (!nameChild || !valueChild) {
+            throw new Error(`Parser bug: NamedArg node has ${children.length} children, expected 2`)
+          }
+          const namePrefix = input.slice(nameChild.from, nameChild.to)
+          const name = namePrefix.slice(0, -1) // Remove '='
+          const value = syntaxNodeToEvalNode(valueChild, input, context)
+          return { kind: 'arg', name, value, node: argNode } as const
+        }
+
+        throw new Error(`Parser bug: Unexpected arg node type: ${argNode.type.name}`)
+      })
+
+      return { kind: 'command', name: commandName, args, node }
+    }
   }
 
   throw new RuntimeError(`Unsupported node type "${node.type.name}"`, node.from, node.to)
 }
 
-/* 
-The code below is a...
-SIN AGAINST GOD!
-...but it makes it easier to use above
-*/
-type ExpectedType = '*' | number
-function destructure(node: SyntaxNode, expected: [ExpectedType]): [SyntaxNode]
-function destructure(
-  node: SyntaxNode,
-  expected: [ExpectedType, ExpectedType]
-): [SyntaxNode, SyntaxNode]
-function destructure(
-  node: SyntaxNode,
-  expected: [ExpectedType, ExpectedType, ExpectedType]
-): [SyntaxNode, SyntaxNode, SyntaxNode]
-function destructure(node: SyntaxNode, expected: ExpectedType[]): SyntaxNode[] {
+// Helper functions for extracting node parts
+const getAllChildren = (node: SyntaxNode): SyntaxNode[] => {
   const children: SyntaxNode[] = []
   let child = node.firstChild
   while (child) {
     children.push(child)
     child = child.nextSibling
   }
+  return children
+}
 
-  if (children.length !== expected.length) {
+const getBinaryParts = (node: SyntaxNode) => {
+  const children = getAllChildren(node)
+  const [left, op, right] = children
+
+  if (!left || !op || !right) {
+    throw new RuntimeError(`BinOp expected 3 children, got ${children.length}`, node.from, node.to)
+  }
+
+  return { left, op, right }
+}
+
+const getAssignmentParts = (node: SyntaxNode) => {
+  const children = getAllChildren(node)
+  const [identifier, _equals, value] = children
+
+  if (!identifier || !_equals || !value) {
     throw new RuntimeError(
-      `${node.type.name} expected ${expected.length} children, got ${children.length}`,
+      `Assignment expected 3 children, got ${children.length}`,
       node.from,
       node.to
     )
   }
 
-  children.forEach((child, i) => {
-    const expectedType = expected[i]
-    if (expectedType !== '*' && child.type.id !== expectedType) {
-      throw new RuntimeError(
-        `Child ${i} of ${node.type.name} expected ${expectedType}, got ${child.type.id} (${child.type.name})`,
-        child.from,
-        child.to
-      )
-    }
-  })
-
-  return children
+  return { identifier, value }
+}
+
+const getParenParts = (node: SyntaxNode) => {
+  const children = getAllChildren(node)
+  const [_leftParen, expr, _rightParen] = children
+
+  if (!_leftParen || !expr || !_rightParen) {
+    throw new RuntimeError(
+      `ParenExpr expected 3 children, got ${children.length}`,
+      node.from,
+      node.to
+    )
+  }
+
+  return expr
+}
+
+const extractCommand = (node: SyntaxNode, input: string) => {
+  const children = getAllChildren(node)
+  const commandNode = children[0] // The Command node
+
+  if (!commandNode || commandNode.type.id !== terms.Command) {
+    throw new RuntimeError('Invalid command structure', node.from, node.to)
+  }
+
+  const commandName = input.slice(commandNode.firstChild!.from, commandNode.firstChild!.to)
+  const argNodes = children.slice(1) // All the Arg/NamedArg nodes
+  return { commandName, commandNode, argNodes }
 }
diff --git a/src/utils/utils.tsx b/src/utils/utils.tsx
index cd3733e..75eab6f 100644
--- a/src/utils/utils.tsx
+++ b/src/utils/utils.tsx
@@ -23,3 +23,7 @@ export const toElement = (node: any): HTMLElement => {
   render(node, c)
   return c.firstElementChild as HTMLElement
 }
+
+export const assertNever = (x: never): never => {
+  throw new Error(`Unexpected object: ${x}`)
+}