fix: allow dragging all gates + stop waveform recording on edits

- INPUT/CLOCK gates can now be dragged (click-without-move = toggle,
  click-and-drag = move). Uses 4px movement threshold.
- Waveform only records samples on intentional actions (INPUT toggle,
  manual step, simulation tick), not on gate placement/movement/connections.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

css/style.css

@@ -1,5 +1,34 @@
 * { margin: 0; padding: 0; box-sizing: border-box; }
 
+/* ==================== Custom Scrollbar ==================== */
+::-webkit-scrollbar {
+    width: 6px;
+    height: 6px;
+}
+
+::-webkit-scrollbar-track {
+    background: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+    background: #2a2a3a;
+    border-radius: 3px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+    background: #00e59966;
+}
+
+::-webkit-scrollbar-corner {
+    background: transparent;
+}
+
+/* Firefox */
+* {
+    scrollbar-width: thin;
+    scrollbar-color: #2a2a3a transparent;
+}
+
 body {
     font-family: 'Segoe UI', system-ui, sans-serif;
     background: #0a0a0f;

js/events.js

@@ -30,10 +30,20 @@ export function initEvents() {
         state.hoveredGate = state.hoveredPort ? state.hoveredPort.gate : findGateAt(world.x, world.y);
 
         if (state.dragging) {
+            // Detect if mouse actually moved (threshold of 4px to distinguish click vs drag)
+            if (dragStartPos && !dragMoved) {
+                const dx = e.offsetX - dragStartPos.x;
+                const dy = e.offsetY - dragStartPos.y;
+                if (Math.abs(dx) > 4 || Math.abs(dy) > 4) {
+                    dragMoved = true;
+                }
+            }
+            if (dragMoved) {
                 state.dragging.x = world.x - state.dragOffset.x;
                 state.dragging.y = world.y - state.dragOffset.y;
                 evaluateAll();
             }
+        }
 
         canvas.style.cursor = state.placingGate ? 'crosshair'
             : state.hoveredPort ? 'pointer'
@@ -41,9 +51,14 @@ export function initEvents() {
             : 'default';
     });
 
+    let dragStartPos = null;
+    let dragMoved = false;
+
     canvas.addEventListener('mousedown', e => {
         if (e.button !== 0) return;
         const world = screenToWorld(e.offsetX, e.offsetY);
+        dragStartPos = { x: e.offsetX, y: e.offsetY };
+        dragMoved = false;
 
         // Placing a new gate
         if (state.placingGate) {
@@ -81,15 +96,8 @@ export function initEvents() {
 
         if (state.connecting) { state.connecting = null; return; }
 
-        // Toggle INPUT/CLOCK
+        // Drag any gate (including INPUT/CLOCK)
         const gate = findGateAt(world.x, world.y);
-        if (gate && (gate.type === 'INPUT' || gate.type === 'CLOCK')) {
-            gate.value = gate.value ? 0 : 1;
-            evaluateAll();
-            return;
-        }
-
-        // Drag gate
         if (gate) {
             state.dragging = gate;
             state.dragOffset = { x: world.x - gate.x, y: world.y - gate.y };
@@ -97,7 +105,18 @@ export function initEvents() {
         }
     });
 
-    canvas.addEventListener('mouseup', () => { state.dragging = null; });
+    canvas.addEventListener('mouseup', e => {
+        // Toggle INPUT/CLOCK only on click (no drag movement)
+        if (state.dragging && !dragMoved) {
+            const gate = state.dragging;
+            if (gate.type === 'INPUT' || gate.type === 'CLOCK') {
+                gate.value = gate.value ? 0 : 1;
+                evaluateAll(true);  // record waveform on intentional toggle
+            }
+        }
+        state.dragging = null;
+        dragStartPos = null;
+    });
 
     canvas.addEventListener('contextmenu', e => {
         e.preventDefault();

js/gates.js

@@ -53,12 +53,12 @@ export function evaluate(gate, visited = new Set()) {
     return result;
 }
 
-export function evaluateAll() {
+export function evaluateAll(recordWave = false) {
     state.gates.forEach(g => {
         if (g.type !== 'INPUT' && g.type !== 'CLOCK') g.value = 0;
     });
     state.gates.forEach(g => evaluate(g));
-    if (state.recording && state.waveformVisible) recordSample();
+    if (recordWave && state.recording && state.waveformVisible) recordSample();
 }
 
 // Register evaluateAll in waveform to break circular dependency

js/levels.js

@@ -75,6 +75,111 @@ export const LEVELS = [
         hints: ['XOR = (A NAND B) NAND (NOT(A NAND NOT B) NAND NOT(NOT A NAND B))', 'This requires 4-5 NAND gates.'],
         difficulty: 3
     },
+    {
+        id: 'xnor_gate',
+        category: 'Logic Basics',
+        title: 'XNOR Gate',
+        description: 'Build an XNOR gate. True when both inputs are equal.',
+        availableGates: ['INPUT', 'OUTPUT', 'NAND'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 1 } },
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 1 } }
+        ],
+        hints: ['XNOR is the inverse of XOR.', 'Build XOR first, then invert the output with another NAND-as-NOT.'],
+        difficulty: 3
+    },
+    // ============ Combinational Logic ============
+    {
+        id: 'mux_2to1',
+        category: 'Combinational Logic',
+        title: '2:1 Multiplexer',
+        description: 'Build a MUX. When SEL=0, output A. When SEL=1, output B. Three inputs: A (0), B (1), SEL (2).',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'OR', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0 } },  // SEL=0 → A=0
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 1 } },  // SEL=0 → A=1
+            { inputs: { 0: 0, 1: 1, 2: 0 }, outputs: { 0: 0 } },  // SEL=0 → A=0
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 1 } },  // SEL=0 → A=1
+            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 0 } },  // SEL=1 → B=0
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 1 } },  // SEL=1 → B=1
+            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 0 } },  // SEL=1 → B=0
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1 } }   // SEL=1 → B=1
+        ],
+        hints: ['MUX = (A AND NOT SEL) OR (B AND SEL).', 'You need 1 NOT, 2 AND, and 1 OR gate.'],
+        difficulty: 2
+    },
+    {
+        id: 'demux_1to2',
+        category: 'Combinational Logic',
+        title: '1:2 Demultiplexer',
+        description: 'Route input to one of two outputs based on SEL. Inputs: DATA (0), SEL (1). Outputs: Q0, Q1.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 0, 1: 0 } },  // DATA=0, SEL=0 → Q0=0, Q1=0
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1, 1: 0 } },  // DATA=1, SEL=0 → Q0=1, Q1=0
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 0, 1: 0 } },  // DATA=0, SEL=1 → Q0=0, Q1=0
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 1 } }   // DATA=1, SEL=1 → Q0=0, Q1=1
+        ],
+        hints: ['Q0 = DATA AND NOT SEL. Q1 = DATA AND SEL.', 'You need 1 NOT and 2 AND gates.'],
+        difficulty: 2
+    },
+    {
+        id: 'and3',
+        category: 'Combinational Logic',
+        title: '3-input AND',
+        description: 'Build a 3-input AND gate. Output is 1 only when all three inputs are 1.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1 } }
+        ],
+        hints: ['Chain two AND gates: (A AND B) AND C.'],
+        difficulty: 1
+    },
+    {
+        id: 'majority',
+        category: 'Combinational Logic',
+        title: 'Majority Gate',
+        description: 'Output 1 if at least two of the three inputs are 1.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'OR'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 0, 1: 1, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 1 } },
+            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 1 } },
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 1 } },
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1 } }
+        ],
+        hints: ['Majority = (A AND B) OR (A AND C) OR (B AND C).', 'You need 3 AND gates and 2 OR gates.'],
+        difficulty: 2
+    },
+    {
+        id: 'parity',
+        category: 'Combinational Logic',
+        title: 'Even Parity',
+        description: 'Output 1 if an even number of inputs are 1 (0 counts as even). Three inputs.',
+        availableGates: ['INPUT', 'OUTPUT', 'XOR', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 1 } },  // 0 ones = even
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 0 } },  // 1 one = odd
+            { inputs: { 0: 0, 1: 1, 2: 0 }, outputs: { 0: 0 } },
+            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 0 } },
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 1 } },  // 2 ones = even
+            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 1 } },
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 1 } },
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 0 } }   // 3 ones = odd
+        ],
+        hints: ['XOR gives odd parity. Invert it for even parity.', 'Chain: NOT(A XOR B XOR C).'],
+        difficulty: 2
+    },
+    // ============ Arithmetic ============
     {
         id: 'half_adder',
         category: 'Arithmetic',
@@ -82,10 +187,10 @@ export const LEVELS = [
         description: 'Build a half adder. Two outputs: Sum (A XOR B) and Carry (A AND B).',
         availableGates: ['INPUT', 'OUTPUT', 'NAND'],
         testCases: [
-            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 0, 1: 0 } },  // 0+0: sum=0, carry=0
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 0, 1: 0 } },
-            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 1, 1: 0 } },  // 0+1: sum=1, carry=0
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 1, 1: 0 } },
-            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1, 1: 0 } },  // 1+0: sum=1, carry=0
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1, 1: 0 } },
-            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 1 } }   // 1+1: sum=0, carry=1
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 1 } }
         ],
         hints: ['Two independent functions: Sum=XOR, Carry=AND.', 'You need 2 OUTPUT gates.'],
         difficulty: 3
@@ -94,36 +199,131 @@ export const LEVELS = [
         id: 'full_adder',
         category: 'Arithmetic',
         title: 'Full Adder',
-        description: 'Build a full adder with carry-in. Outputs: Sum (3-input XOR) and Carry.',
+        description: 'Build a full adder with carry-in. Outputs: Sum and Carry-out.',
         availableGates: ['INPUT', 'OUTPUT', 'NAND'],
         testCases: [
-            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0, 1: 0 } },  // 0+0+0
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0, 1: 0 } },
-            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 1, 1: 0 } },  // 0+0+1
+            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 1, 1: 0 } },
-            { inputs: { 0: 0, 1: 1, 2: 0 }, outputs: { 0: 1, 1: 0 } },  // 0+1+0
+            { inputs: { 0: 0, 1: 1, 2: 0 }, outputs: { 0: 1, 1: 0 } },
-            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 0, 1: 1 } },  // 0+1+1
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 0, 1: 1 } },
-            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 1, 1: 0 } },  // 1+0+0
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 1, 1: 0 } },
-            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 0, 1: 1 } },  // 1+0+1
+            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 0, 1: 1 } },
-            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 0, 1: 1 } },  // 1+1+0
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 0, 1: 1 } },
-            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1, 1: 1 } }   // 1+1+1
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1, 1: 1 } }
         ],
-        hints: ['Reuse your half adder logic. A full adder = half adder + half adder + OR.'],
+        hints: ['A full adder = two half adders + OR for the carry.', 'Sum = A XOR B XOR Cin. Cout = (A AND B) OR (Cin AND (A XOR B)).'],
         difficulty: 4
     },
+    {
+        id: 'half_subtractor',
+        category: 'Arithmetic',
+        title: 'Half Subtractor',
+        description: 'Build A minus B. Outputs: Difference (A XOR B) and Borrow (NOT A AND B).',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'XOR', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 0, 1: 0 } },  // 0-0: diff=0, borrow=0
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 1, 1: 1 } },  // 0-1: diff=1, borrow=1
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1, 1: 0 } },  // 1-0: diff=1, borrow=0
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 0 } }   // 1-1: diff=0, borrow=0
+        ],
+        hints: ['Difference = A XOR B (same as addition!).', 'Borrow = (NOT A) AND B.'],
+        difficulty: 2
+    },
+    {
+        id: 'comparator',
+        category: 'Arithmetic',
+        title: '1-bit Comparator',
+        description: 'Compare A and B. Three outputs: A>B, A=B, A<B.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'OR', 'NOT', 'XOR'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 0, 1: 1, 2: 0 } },  // 0=0: GT=0, EQ=1, LT=0
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 0, 1: 0, 2: 1 } },  // 0<1: GT=0, EQ=0, LT=1
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1, 1: 0, 2: 0 } },  // 1>0: GT=1, EQ=0, LT=0
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 1, 2: 0 } }   // 1=1: GT=0, EQ=1, LT=0
+        ],
+        hints: ['A>B = A AND NOT B.', 'A=B = NOT(A XOR B) = XNOR.', 'A<B = NOT A AND B.'],
+        difficulty: 3
+    },
+    // ============ Decoders & Encoders ============
+    {
+        id: 'decoder_2to4',
+        category: 'Decoders & Encoders',
+        title: '2-to-4 Decoder',
+        description: 'Decode 2 input bits into 4 output lines. Only one output is 1 at a time.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 1, 1: 0, 2: 0, 3: 0 } },  // 00 → line 0
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 0, 1: 1, 2: 0, 3: 0 } },  // 01 → line 1
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 0, 1: 0, 2: 1, 3: 0 } },  // 10 → line 2
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 0, 1: 0, 2: 0, 3: 1 } }   // 11 → line 3
+        ],
+        hints: ['Q0 = NOT A AND NOT B.', 'Q1 = NOT A AND B. Q2 = A AND NOT B. Q3 = A AND B.', 'You need 2 NOT gates and 4 AND gates.'],
+        difficulty: 3
+    },
+    {
+        id: 'encoder_4to2',
+        category: 'Decoders & Encoders',
+        title: '4-to-2 Encoder',
+        description: 'Encode 4 input lines into 2-bit binary. Assume only one input is active at a time.',
+        availableGates: ['INPUT', 'OUTPUT', 'OR'],
+        testCases: [
+            { inputs: { 0: 1, 1: 0, 2: 0, 3: 0 }, outputs: { 0: 0, 1: 0 } },  // line 0 → 00
+            { inputs: { 0: 0, 1: 1, 2: 0, 3: 0 }, outputs: { 0: 0, 1: 1 } },  // line 1 → 01
+            { inputs: { 0: 0, 1: 0, 2: 1, 3: 0 }, outputs: { 0: 1, 1: 0 } },  // line 2 → 10
+            { inputs: { 0: 0, 1: 0, 2: 0, 3: 1 }, outputs: { 0: 1, 1: 1 } }   // line 3 → 11
+        ],
+        hints: ['Bit 1 (MSB) = Input2 OR Input3.', 'Bit 0 (LSB) = Input1 OR Input3.', 'Just 2 OR gates!'],
+        difficulty: 2
+    },
+    {
+        id: 'seven_seg_a',
+        category: 'Decoders & Encoders',
+        title: '7-Segment: Segment A',
+        description: 'Drive segment A of a 7-segment display for digits 0-3. Segment A is ON for 0, 2, 3.',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'OR', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0 }, outputs: { 0: 1 } },  // 0 → A on
+            { inputs: { 0: 0, 1: 1 }, outputs: { 0: 0 } },  // 1 → A off
+            { inputs: { 0: 1, 1: 0 }, outputs: { 0: 1 } },  // 2 → A on
+            { inputs: { 0: 1, 1: 1 }, outputs: { 0: 1 } }   // 3 → A on
+        ],
+        hints: ['A = NOT(NOT A1 AND A0). Or equivalently: A = A1 OR NOT A0.'],
+        difficulty: 2
+    },
+    // ============ Components ============
     {
         id: 'two_bit_adder',
         category: 'Components',
         title: '2-bit Adder',
         description: 'Chain two full adders to add two 2-bit numbers.',
-        availableGates: ['INPUT', 'OUTPUT', 'FULL_ADDER'],  // FULL_ADDER is saved component
+        availableGates: ['INPUT', 'OUTPUT', 'FULL_ADDER'],
         testCases: [
-            { inputs: { 0: 0, 1: 0, 2: 0, 3: 0 }, outputs: { 0: 0, 1: 0, 2: 0 } },  // 00+00=000
+            { inputs: { 0: 0, 1: 0, 2: 0, 3: 0 }, outputs: { 0: 0, 1: 0, 2: 0 } },
-            { inputs: { 0: 0, 1: 0, 2: 0, 3: 1 }, outputs: { 0: 0, 1: 0, 2: 1 } },  // 00+01=001
+            { inputs: { 0: 0, 1: 0, 2: 0, 3: 1 }, outputs: { 0: 0, 1: 0, 2: 1 } },
-            { inputs: { 0: 0, 1: 1, 2: 0, 3: 1 }, outputs: { 0: 0, 1: 1, 2: 1 } },  // 01+01=010
+            { inputs: { 0: 0, 1: 1, 2: 0, 3: 1 }, outputs: { 0: 0, 1: 1, 2: 1 } },
-            { inputs: { 0: 1, 1: 1, 2: 0, 3: 1 }, outputs: { 0: 1, 1: 1, 2: 1 } },  // 11+01=100
+            { inputs: { 0: 1, 1: 1, 2: 0, 3: 1 }, outputs: { 0: 1, 1: 1, 2: 1 } },
-            { inputs: { 0: 1, 1: 1, 2: 1, 3: 1 }, outputs: { 0: 0, 1: 1, 2: 1 } }   // 11+11=110
+            { inputs: { 0: 1, 1: 1, 2: 1, 3: 1 }, outputs: { 0: 0, 1: 1, 2: 1 } }
         ],
         hints: ['Use two FULL_ADDER components chained together.', 'First adder has no carry-in (set to 0).'],
         difficulty: 3
+    },
+    {
+        id: 'alu_1bit',
+        category: 'Components',
+        title: '1-bit ALU',
+        description: 'Build a 1-bit ALU. OP=0 → AND, OP=1 → OR. Inputs: A (0), B (1), OP (2).',
+        availableGates: ['INPUT', 'OUTPUT', 'AND', 'OR', 'NOT'],
+        testCases: [
+            { inputs: { 0: 0, 1: 0, 2: 0 }, outputs: { 0: 0 } },  // 0 AND 0 = 0
+            { inputs: { 0: 1, 1: 0, 2: 0 }, outputs: { 0: 0 } },  // 1 AND 0 = 0
+            { inputs: { 0: 1, 1: 1, 2: 0 }, outputs: { 0: 1 } },  // 1 AND 1 = 1
+            { inputs: { 0: 0, 1: 0, 2: 1 }, outputs: { 0: 0 } },  // 0 OR 0 = 0
+            { inputs: { 0: 1, 1: 0, 2: 1 }, outputs: { 0: 1 } },  // 1 OR 0 = 1
+            { inputs: { 0: 0, 1: 1, 2: 1 }, outputs: { 0: 1 } },  // 0 OR 1 = 1
+            { inputs: { 0: 1, 1: 1, 2: 1 }, outputs: { 0: 1 } }   // 1 OR 1 = 1
+        ],
+        hints: ['Compute both A AND B and A OR B, then use a MUX to select based on OP.', 'MUX = (result0 AND NOT OP) OR (result1 AND OP).'],
+        difficulty: 3
     }
 ];