diff --git a/plonky2_verifier/noop_gate.go b/plonky2_verifier/noop_gate.go
new file mode 100644
index 0000000..3855197
--- /dev/null
+++ b/plonky2_verifier/noop_gate.go
@@ -0,0 +1,12 @@
+package plonky2_verifier
+
+import (
+	. "gnark-plonky2-verifier/field"
+)
+
+type NoopGate struct {
+}
+
+func (p *NoopGate) EvalUnfiltered(pc *PlonkChip, vars EvaluationVars) []QuadraticExtension {
+	return []QuadraticExtension{}
+}
diff --git a/plonky2_verifier/poseidon_gate.go b/plonky2_verifier/poseidon_gate.go
new file mode 100644
index 0000000..3980fc9
--- /dev/null
+++ b/plonky2_verifier/poseidon_gate.go
@@ -0,0 +1,156 @@
+package plonky2_verifier
+
+import (
+	. "gnark-plonky2-verifier/field"
+	"gnark-plonky2-verifier/poseidon"
+)
+
+func (g *PoseidonGate) WireInput(i uint64) uint64 {
+	return i
+}
+
+func (g *PoseidonGate) WireOutput(i uint64) uint64 {
+	return poseidon.SPONGE_WIDTH + i
+}
+
+func (g *PoseidonGate) WireSwap() uint64 {
+	return 2 * poseidon.SPONGE_WIDTH
+}
+
+const START_DELTA = 2*poseidon.SPONGE_WIDTH + 1
+
+func (g *PoseidonGate) WireDelta(i uint64) uint64 {
+	if i >= 4 {
+		panic("Delta index out of range")
+	}
+	return START_DELTA + i
+}
+
+const START_FULL_0 = START_DELTA + 4
+
+func (g *PoseidonGate) WireFullSBox0(round uint64, i uint64) uint64 {
+	if round == 0 {
+		panic("First-round S-box inputs are not stored as wires")
+	}
+	if round >= poseidon.HALF_N_FULL_ROUNDS {
+		panic("S-box input round out of range")
+	}
+	if i >= poseidon.SPONGE_WIDTH {
+		panic("S-box input index out of range")
+	}
+
+	return START_FULL_0 + (round-1)*poseidon.SPONGE_WIDTH + i
+}
+
+const START_PARTIAL = START_FULL_0 + (poseidon.HALF_N_FULL_ROUNDS-1)*poseidon.SPONGE_WIDTH
+
+func (g *PoseidonGate) WirePartialSBox(round uint64) uint64 {
+	if round >= poseidon.N_PARTIAL_ROUNDS {
+		panic("S-box input round out of range")
+	}
+	return START_PARTIAL + round
+}
+
+const START_FULL_1 = START_PARTIAL + poseidon.N_PARTIAL_ROUNDS
+
+func (g *PoseidonGate) WireFullSBox1(round uint64, i uint64) uint64 {
+	if round >= poseidon.HALF_N_FULL_ROUNDS {
+		panic("S-box input round out of range")
+	}
+	if i >= poseidon.SPONGE_WIDTH {
+		panic("S-box input index out of range")
+	}
+
+	return START_FULL_1 + round*poseidon.SPONGE_WIDTH + i
+}
+
+func (g *PoseidonGate) WiresEnd() uint64 {
+	return START_FULL_1 + poseidon.HALF_N_FULL_ROUNDS*poseidon.SPONGE_WIDTH
+}
+
+type PoseidonGate struct {
+}
+
+func (p *PoseidonGate) EvalUnfiltered(pc *PlonkChip, vars EvaluationVars) []QuadraticExtension {
+	constraints := []QuadraticExtension{}
+
+	// Assert that `swap` is binary.
+	swap := vars.localWires[p.WireSwap()]
+	notSwap := pc.qeAPI.SubExtension(pc.qeAPI.FieldToQE(ONE_F), swap)
+	constraints = append(constraints, pc.qeAPI.MulExtension(swap, notSwap))
+
+	// Assert that each delta wire is set properly: `delta_i = swap * (rhs - lhs)`.
+	for i := uint64(0); i < 4; i++ {
+		inputLhs := vars.localWires[p.WireInput(i)]
+		inputRhs := vars.localWires[p.WireInput(i+4)]
+		deltaI := vars.localWires[p.WireDelta(i)]
+		diff := pc.qeAPI.SubExtension(inputRhs, inputLhs)
+		expectedDeltaI := pc.qeAPI.MulExtension(swap, diff)
+		constraints = append(constraints, pc.qeAPI.SubExtension(expectedDeltaI, deltaI))
+	}
+
+	// Compute the possibly-swapped input layer.
+	state := make([]QuadraticExtension, poseidon.SPONGE_WIDTH)
+	for i := uint64(0); i < 4; i++ {
+		deltaI := vars.localWires[p.WireDelta(i)]
+		inputLhs := vars.localWires[p.WireInput(i)]
+		inputRhs := vars.localWires[p.WireInput(i+4)]
+		state[i] = pc.qeAPI.AddExtension(inputLhs, deltaI)
+		state[i+4] = pc.qeAPI.SubExtension(inputRhs, deltaI)
+	}
+	for i := uint64(8); i < poseidon.SPONGE_WIDTH; i++ {
+		state[i] = vars.localWires[p.WireInput(i)]
+	}
+
+	round_ctr := 0
+
+	// First set of full rounds.
+	for r := uint64(0); r < poseidon.HALF_N_FULL_ROUNDS; r++ {
+		// TODO: constantLayerField(state, round_ctr)
+		if r != 0 {
+			for i := uint64(0); i < poseidon.SPONGE_WIDTH; i++ {
+				sBoxIn := vars.localWires[p.WireFullSBox0(r, i)]
+				constraints = append(constraints, pc.qeAPI.SubExtension(state[i], sBoxIn))
+				state[i] = sBoxIn
+			}
+		}
+		// TODO: sboxLayerField(state)
+		// TODO: state = mdsLayerField(state)
+		round_ctr++
+	}
+
+	// Partial rounds.
+	// TODO: partialFirstConstantLayer(state)
+	// TODO: state = mdsParitalLayerInit(state)
+	for r := uint64(0); r < poseidon.N_PARTIAL_ROUNDS-1; r++ {
+		sBoxIn := vars.localWires[p.WirePartialSBox(r)]
+		constraints = append(constraints, pc.qeAPI.SubExtension(state[0], sBoxIn))
+		// TODO: state[0] = sBoxMonomial(sBoxIn)
+		// TODO: state[0] += NewFieldElement(FAST_PARTIAL_ROUND_CONSTANTS[r])
+		// TODO: state = mdsParitalLayerFastField(state, r)
+	}
+	sBoxIn := vars.localWires[p.WirePartialSBox(poseidon.N_PARTIAL_ROUNDS-1)]
+	constraints = append(constraints, pc.qeAPI.SubExtension(state[0], sBoxIn))
+	// TODO: state[0] = sBoxMonomial(sBoxIn)
+	// TODO: state = mdsPartialLayerLastField(state, poseidon.N_PARTIAL_ROUNDS - 1)
+	round_ctr += poseidon.N_PARTIAL_ROUNDS
+
+	// Second set of full rounds.
+	for r := uint64(0); r < poseidon.HALF_N_FULL_ROUNDS; r++ {
+		// TODO: constantLayerField(state, round_ctr)
+		for i := uint64(0); i < poseidon.SPONGE_WIDTH; i++ {
+			sBoxIn := vars.localWires[p.WireFullSBox1(r, i)]
+			constraints = append(constraints, pc.qeAPI.SubExtension(state[i], sBoxIn))
+			state[i] = sBoxIn
+		}
+		// TODO: sboxLayerField(state)
+		// TODO: state = mdsLayerField(state)
+		round_ctr++
+	}
+
+	for i := uint64(0); i < poseidon.SPONGE_WIDTH; i++ {
+		constraints = append(constraints, pc.qeAPI.SubExtension(state[i], vars.localWires[p.WireOutput(i)]))
+	}
+
+	return constraints
+}
diff --git a/plonky2_verifier/public_input_gate.go b/plonky2_verifier/public_input_gate.go
new file mode 100644
index 0000000..1804560
--- /dev/null
+++ b/plonky2_verifier/public_input_gate.go
@@ -0,0 +1,28 @@
+package plonky2_verifier
+
+import (
+	. "gnark-plonky2-verifier/field"
+)
+
+type PublicInputGate struct {
+}
+
+func (g *PublicInputGate) WiresPublicInputsHash() []uint64 {
+	return []uint64{0, 1, 2, 3}
+}
+
+func (p *PublicInputGate) EvalUnfiltered(pc *PlonkChip, vars EvaluationVars) []QuadraticExtension {
+	constraints := []QuadraticExtension{}
+
+	wires := p.WiresPublicInputsHash()
+	hash_parts := vars.publicInputsHash
+	for i := 0; i < 4; i++ {
+		wire := wires[i]
+		hash_part := hash_parts[i]
+
+		diff := pc.qeAPI.SubExtension(vars.localWires[wire], pc.qeAPI.FieldToQE(hash_part))
+		constraints = append(constraints, diff)
+	}
+
+	return constraints
+}