diff --git a/src/main.zig b/src/main.zig
index ae66d5b..9f10d7a 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -5,8 +5,17 @@ pub fn main() !void {
     defer _ = gpa.deinit();
     // const allocator = gpa.allocator();
 
-    // var input = Wire{ .digital = false, .analog = 1.0 };
-    // var input_buffer = Not{ .invert_output = false, .input = &input };
+    var input = Signal{ .digital = 1, .analog = 1.0 };
+
+    var not1 = Not{ .input = &input };
+    var not2 = Not{ .input = &not1.output, .invert_output = false };
+    var not3 = Not{ .input = &not2.output };
+
+    not1.process();
+    not2.process();
+    not3.process();
+
+    std.debug.print("{}\n{}\n{}\n{}\n", .{ input, not1.output, not2.output, not3.output });
 
     // // analog in
     // var wire1 = Wire{};
@@ -78,13 +87,44 @@ pub const Component = struct {
     x: u16 = 0,
     y: u16 = 0,
 
-    processFn: *const fn (*Component) void,
+    processFn: *const fn (*Component, []*Signal) []Signal,
+};
+
+pub const Signal = struct {
+    digital: i2 = 0,
+    analog: f32 = 0.0,
+    color: u24 = 0,
+
+    pub fn format(
+        self: Signal,
+        comptime fmt: []const u8,
+        options: std.fmt.FormatOptions,
+        writer: anytype,
+    ) !void {
+        _ = .{ fmt, options };
+        try writer.writeAll("Signal(");
+        if (self.digital < 0) try writer.writeByte('-') else try writer.writeByte('+');
+        try writer.print("{d} / {d:0>1.4})", .{
+            @abs(self.digital),
+            self.analog,
+        });
+    }
 };
 
 pub const Circuit = struct {
     width: u16 = 8,
     height: u16 = 8,
     components: std.ArrayList(Component),
+
+    pub fn init(allocator: std.mem.Allocator) Circuit {
+        return .{
+            .components = std.ArrayList(Component).init(allocator),
+        };
+    }
+
+    pub fn deinit(self: *Circuit) void {
+        self.components.deinit();
+    }
 };
 
 pub const Battery = struct {
@@ -101,12 +141,6 @@ pub const Battery = struct {
     }
 };
 
-pub const Signal = struct {
-    digital: i2 = 0,
-    analog: f32 = 0.0,
-    color: u24 = 0,
-};
-
 // pub const Wire = struct {
 //     digital: bool = false,
 //     analog: f32 = 0.0,
@@ -143,24 +177,25 @@ pub const Signal = struct {
 //     }
 // };
 
-// pub const Not = struct {
-//     // component: Component = .{},
+pub const Not = struct {
+    // component: Component = .{},
 
-//     input: *Wire,
-//     output: *Wire,
+    input: *Signal,
+    output: Signal = .{},
 
-//     invert_output: bool = true,
+    invert_output: bool = true,
 
-//     pub fn process(self: *Not) void {
-//         if (self.invert_output) {
-//             self.output.digital = !self.input.digital;
-//             self.output.analogSet(1.0 - @abs(self.input.analog));
-//         } else {
-//             self.output.digital = self.input.digital;
-//             self.output.analogSet(self.input.analog); // TODO does the output get clamped here?
-//         }
-//     }
-// };
+    pub fn process(self: *Not) void {
+        if (self.invert_output) {
+            self.output.digital = -self.input.digital;
+            self.output.analog = 1.0 - @abs(self.input.analog);
+        } else {
+            self.output.digital = self.input.digital;
+            self.output.analog = self.input.analog;
+        }
+        self.output.analog = std.math.clamp(self.output.analog, 0.0, 1.0);
+    }
+};
 
 // pub const And = struct {
 //     // component: Component,