diff --git a/02/src/main.zig b/02/src/main.zig
index 270da8c..45b6022 100644
--- a/02/src/main.zig
+++ b/02/src/main.zig
@@ -5,7 +5,9 @@ fn run(program: []i32, noun: i32, verb: i32) i32 {
     program[1] = noun;
     program[2] = verb;
 
-    intcode.run(program);
+    var machine = &intcode.Machine{ .memory = program, .ip = 0 };
+
+    machine.run();
 
     return program[0];
 }
diff --git a/lib/intcode/intcode.zig b/lib/intcode/intcode.zig
index 95a546d..661f8ac 100644
--- a/lib/intcode/intcode.zig
+++ b/lib/intcode/intcode.zig
@@ -27,86 +27,101 @@ pub fn loadFromStdIn(alloc: *std.mem.Allocator) anyerror![]i32 {
     return loadFromStream(alloc, stream);
 }
 
-pub fn run(program: []i32) void {
-    // Initial program state
-    var ip: u32 = 0;
-    var exit: bool = false;
+pub const Machine = struct {
+    memory: []i32,
 
-    // TODO: create a nice struct
+    ip: usize = 0,
 
-    while (!exit) {
-        //        std.debug.warn(" IP {d:4}: ", ip);
-        const opcode = switch (program[ip]) {
+    pub fn Run(program: []i32) anyerror!Machine {
+        var machine = try init(program);
+
+        machine.run();
+
+        return machine;
+    }
+
+    pub fn init(program: []i32) anyerror!Machine {
+        return Machine{ .memory = program };
+    }
+
+    pub fn run(self: *Machine) void {
+        while (self.step()) {}
+    }
+
+    pub fn step(self: *Machine) bool {
+        var program = self.memory;
+
+        const opcode = switch (program[self.ip]) {
             1 => {
-                var a = program[@intCast(usize, program[ip + 1])];
-                var b = program[@intCast(usize, program[ip + 2])];
-                var dest = program[ip + 3];
+                var a = program[@intCast(usize, program[self.ip + 1])];
+                var b = program[@intCast(usize, program[self.ip + 2])];
+                var dest = program[self.ip + 3];
                 var result = a + b;
 
-                //                std.debug.warn("ADD:  [{}] + [{}] => {} : {} + {} = {} => {}\n", ip + 1, ip + 2, dest, a, b, result, dest);
                 program[@intCast(usize, dest)] = result;
-                ip += 4;
+                self.ip += 4;
             },
             2 => {
-                var a = program[@intCast(usize, program[ip + 1])];
-                var b = program[@intCast(usize, program[ip + 2])];
-                var dest = program[ip + 3];
+                var a = program[@intCast(usize, program[self.ip + 1])];
+                var b = program[@intCast(usize, program[self.ip + 2])];
+                var dest = program[self.ip + 3];
                 var result = a * b;
 
-                //                std.debug.warn("MULT: [{}] + [{}] => {} : {} + {} = {} => {}\n", ip + 1, ip + 2, dest, a, b, result, dest);
                 program[@intCast(usize, dest)] = result;
-                ip += 4;
+                self.ip += 4;
             },
             99 => {
-                //                std.debug.warn("EXIT\n");
-                exit = true;
+                self.ip += 1;
+                return false;
             },
             else => {
-                std.debug.warn("Unknown opcode at IP {}: {}", ip, program[ip]);
-                exit = true;
+                std.debug.warn("Unknown opcode at IP {}: {}", self.ip, program[self.ip]);
+                return false;
             },
         };
+
+        return true;
     }
-}
+};
 
 const assert = std.debug.assert;
 
 test "day 2 example 1" {
     var before: [12]i32 = .{ 1, 9, 10, 3, 2, 3, 11, 0, 99, 30, 40, 50 };
     var after: [12]i32 = .{ 3500, 9, 10, 70, 2, 3, 11, 0, 99, 30, 40, 50 };
+    var machine = Machine.Run(before[0..before.len]);
 
-    run(before[0..before.len]);
     assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
 }
 
 test "day 2 example 2" {
     var before: [5]i32 = .{ 1, 0, 0, 0, 99 };
     var after: [5]i32 = .{ 2, 0, 0, 0, 99 };
+    var machine = Machine.Run(before[0..before.len]);
 
-    run(before[0..before.len]);
     assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
 }
 
 test "day 2 example 3" {
     var before: [5]i32 = .{ 2, 3, 0, 3, 99 };
     var after: [5]i32 = .{ 2, 3, 0, 6, 99 };
+    var machine = Machine.Run(before[0..before.len]);
 
-    run(before[0..before.len]);
     assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
 }
 
 test "day 2 example 4" {
     var before: [6]i32 = .{ 2, 4, 4, 5, 99, 0 };
     var after: [6]i32 = .{ 2, 4, 4, 5, 99, 9801 };
+    var machine = Machine.Run(before[0..before.len]);
 
-    run(before[0..before.len]);
     assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
 }
 
 test "day 2 example 5" {
     var before: [9]i32 = .{ 1, 1, 1, 4, 99, 5, 6, 0, 99 };
     var after: [9]i32 = .{ 30, 1, 1, 4, 2, 5, 6, 0, 99 };
+    var machine = Machine.Run(before[0..before.len]);
 
-    run(before[0..before.len]);
     assert(std.mem.eql(i32, before[0..before.len], after[0..after.len]));
 }