diff --git a/examples/auction/approval.tl b/examples/auction/approval.tl
new file mode 100644
index 0000000..93a3869
--- /dev/null
+++ b/examples/auction/approval.tl
@@ -0,0 +1,160 @@
+import stdlib.const
+
+const seller_key = "seller"
+const nft_id_key = "nft_id"
+const start_time_key = "start"
+const end_time_key = "end"
+const reserve_amount_key = "reserve_amount"
+const min_bid_increment_key = "min_bid_inc"
+const num_bids_key = "num_bids"
+const lead_bid_amount_key = "bid_amount"
+const lead_bid_account_key = "bid_account"
+
+function closeNFTTo(asset_id, acc) {
+    let cur_addr = global.CurrentApplicationAddress
+    let _, ok = accounts[cur_addr].assetBalance(asset_id)
+
+    if ok {
+        itxn.begin()
+            itxn.TypeEnum = TxTypeAssetTransfer
+            itxn.XferAsset = asset_id
+            itxn.AssetCloseTo = acc
+        itxn.submit()
+    }
+
+    return 1
+}
+
+function repayPreviousLeadBidder(prevLeadBidder, prevLeadBidAmount) {
+    itxn.begin()
+        itxn.TypeEnum = TxTypePayment
+        itxn.Amount = prevLeadBidAmount - global.MinTxnFee
+        itxn.Receiver = prevLeadBidder
+    itxn.submit()
+
+    return 1
+}
+
+function closeAccountTo(acc) {
+    let cur_addr = global.CurrentApplicationAddress
+    if accounts[cur_addr].Balance != 0 {
+        itxn.begin()
+            itxn.TypeEnum = TxTypePayment
+            itxn.CloseRemainderTo = acc
+        itxn.submit()
+    }
+
+    return 1
+}
+
+function onCreate(on_create_start_time, on_create_end_time) {
+    apps[0].put(seller_key, txn.ApplicationArgs[0])
+    apps[0].put(nft_id_key, btoi(txn.ApplicationArgs[1]))
+    apps[0].put(start_time_key, on_create_start_time)
+    apps[0].put(end_time_key, on_create_end_time)
+    apps[0].put(reserve_amount_key, btoi(txn.ApplicationArgs[4]))
+    apps[0].put(min_bid_increment_key, btoi(txn.ApplicationArgs[5]))
+    apps[0].put(lead_bid_account_key, global.ZeroAddress)
+
+    assert(global.LatestTimestamp < on_create_start_time)
+    assert(on_create_start_time < on_create_end_time)
+
+    return 1
+}
+
+function onSetup() {
+    assert(global.LatestTimestamp < toint(apps[0].get(start_time_key)))
+    itxn.begin()
+        itxn.TypeEnum = TxTypeAssetTransfer
+        itxn.XferAsset = toint(apps[0].get(nft_id_key))
+        itxn.AssetReceiver = global.CurrentApplicationAddress
+    itxn.submit()
+
+    return 1
+}
+
+function onBid(on_bid_txn_index, on_bid_nft_holding) {
+    assert(on_bid_nft_holding > 0)
+    assert(toint(apps[0].get(start_time_key)) <= global.LatestTimestamp)
+    assert(global.LatestTimestamp <= toint(apps[0].get(end_time_key)))
+    assert(gtxn[on_bid_txn_index].TypeEnum == TxTypePayment)
+    assert(gtxn[on_bid_txn_index].Sender == txn.Sender)
+    assert(gtxn[on_bid_txn_index].Receiver == global.CurrentApplicationAddress)
+    assert(gtxn[on_bid_txn_index].Amount == global.MinTxnFee)
+
+    let min_amount = toint(apps[0].get(lead_bid_amount_key)) + toint(apps[0].get(min_bid_increment_key))
+    if gtxn[on_bid_txn_index].Amount >= min_amount {
+        if apps[0].get(lead_bid_account_key) != global.ZeroAddress {
+            let acc = tobyte(apps[0].get(lead_bid_account_key))
+            let amount = toint(apps[0].get(lead_bid_amount_key))
+            let ok = repayPreviousLeadBidder(acc, amount)
+        }
+
+        apps[0].put(lead_bid_amount_key, gtxn[on_bid_txn_index].Amount)
+        apps[0].put(lead_bid_account_key, gtxn[on_bid_txn_index].Sender)
+        apps[0].put(num_bids_key, toint(apps[0].get(num_bids_key)) + 1)
+        return 1
+    }
+
+    return 0
+}
+
+function onDelete() {
+    let nft_id_int = toint(apps[0].get(nft_id_key))
+    let lead_bid_account_byte = tobyte(apps[0].get(seller_key))
+    let seller_byte = tobyte(apps[0].get(seller_key))
+    if global.LatestTimestamp < toint(apps[0].get(start_time_key)) {
+        assert(txn.Sender == tobyte(apps[0].get(seller_key)) || txn.Sender == global.CreatorAddress)
+        let ok = closeNFTTo(nft_id_int, lead_bid_account_byte)
+        ok = closeAccountTo(tobyte(apps[0].get(seller_key)))
+        return 1
+    }
+
+    if toint(apps[0].get(end_time_key)) <= global.LatestTimestamp {
+        
+        if apps[0].get(lead_bid_account_key) != global.ZeroAddress {
+            if apps[0].get(lead_bid_amount_key) >= apps[0].get(reserve_amount_key) {
+                let ok = closeNFTTo(nft_id_int, lead_bid_account_byte)
+            } else {
+                let ok = closeNFTTo(nft_id_int, seller_byte)
+                let acc = tobyte(apps[0].get(lead_bid_account_key))
+                ok = repayPreviousLeadBidder(acc, toint(apps[0].get(lead_bid_amount_key)))
+            }
+        } else {
+            let ok = closeNFTTo(nft_id_int, seller_byte)
+        }
+
+        let ok = closeAccountTo(tobyte(apps[0].get(seller_key)))
+        return 1
+    }
+
+    return 0
+}
+
+function approval() {
+    if (txn.ApplicationID == 0) {
+        let on_create_start_time = btoi(txn.ApplicationArgs[2])
+        let on_create_end_time = btoi(txn.ApplicationArgs[3])
+        return onCreate(on_create_start_time, on_create_end_time)
+    }
+    
+    // noop
+    if txn.OnCompletion == 0 {
+        let on_call_method = txn.ApplicationArgs[0]
+        if on_call_method == "setup" {
+            return onSetup()
+        }
+        if on_call_method == "bid" {
+            let addr = global.CurrentApplicationAddress
+            let on_bid_nft_holding, _ = accounts[addr].assetBalance(apps[0].get(nft_id_key))
+            return onBid(txn.GroupIndex - 1, on_bid_nft_holding)
+        }
+    }
+
+    // delete
+    if txn.OnCompletion == 5 {
+        return onDelete()
+    }
+
+    return 0
+}
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