diff --git a/index.js b/index.js
index d25511e..d4b3794 100644
--- a/index.js
+++ b/index.js
@@ -679,22 +679,46 @@ function lower(ast) {
     assert(!Number.isNaN(ctx.offset));
     const { ib, variables } = ctx;
     switch (expr.kind) {
-      case "call": {
-        if (expr.lhs.kind !== "ident") {
-          throw new Error("bad");
-        }
-        if (expr.args.length !== 1) {
-          throw new Error("bad");
-        }
+        case "call": {
+          // Handle function calls with arguments
+          if (expr.lhs.kind !== "ident") {
+            throw new Error("unsupported call target");
+          }
+          if (expr.args.length > 4) {
+            throw new Error("too many arguments");
+          }
 
-        // TODO: save
-        codegenExpr(ctx, expr.args[0]);
-        // mov edi, eax
-        ib.movRegReg32(REG_DI, REG_A);
-        ib.call(expr.lhs.string);
+          // Generate code for arguments in reverse order (right-to-left)
+          for (let i = expr.args.length - 1; i >= 0; i--) {
+            const arg = expr.args[i];
+            // If argument is a comma expression, use just the right side
+            if (arg.kind === ",") {
+              codegenExpr(ctx, arg.rhs);
+            } else {
+              codegenExpr(ctx, arg);
+            }
+            
+            // Move result to correct parameter register
+            switch (i) {
+              case 0:
+                ib.movRegReg32(REG_DI, REG_A);
+                break;
+              case 1:
+                ib.movRegReg32(REG_SI, REG_A);
+                break;
+              case 2:
+                ib.movRegReg32(REG_D, REG_A);
+                break;
+              case 3:
+                ib.movRegReg32(REG_C, REG_A);
+                break;
+            }
+          }
 
-        break;
-      }
+          ib.call(expr.lhs.string);
+
+          break;
+        }
       case "integer": {
         ib.movEaxImm32(expr.integer);
         break;
@@ -707,6 +731,22 @@ function lower(ast) {
         ib.movStackOffsetToReg(offset.stackOffset + ctx.offset, REG_A);
         break;
       }
+      case "=": {
+        // For assignment operations, generate code for RHS
+        codegenExpr(ctx, expr.rhs);
+        
+        // Find the variable to assign to
+        const varOffset = [...variables]
+          .reverse()
+          .find((v) => v.name === expr.lhs.string);
+        if (!varOffset) {
+          throw new Error(`undefined variable: ${expr.lhs.string}`);
+        }
+        
+        // Store the result (in eax) to the variable's stack location
+        ib.movRegToStackOffset(varOffset.stackOffset + ctx.offset, REG_A);
+        break;
+      }
       case "+": {
         // For binary expressions, we first evaluate the LHS, save it on the stack,
         // evaluate the RHS, then restore the LHS and perform the operation.
@@ -741,7 +781,7 @@ function lower(ast) {
 
     func.params.forEach((param, i) => {
       assert(param.type.kind === "int");
-      const offset = ib.reserveStack(4);
+      const offset = ib.reserveStack(8); // Use 8 bytes for 64-bit values
       ib.movRegToStackOffset(offset, PARAM_CALLCONV_REGISTERS[i]);
       variables.push({
         name: param.name,
@@ -769,7 +809,7 @@ function lower(ast) {
           if (stmt.init) {
             codegenExpr(ctx, stmt.init);
           }
-          const slot = ib.reserveStack(4);
+          const slot = ib.reserveStack(8); // Use 8 bytes for 64-bit values
           variables.push({
             name: stmt.name,
             stackOffset: slot,