diff --git a/beacon_chain_impl/bls.py b/beacon_chain_impl/bls.py
new file mode 100644
index 0000000..7a26edd
--- /dev/null
+++ b/beacon_chain_impl/bls.py
@@ -0,0 +1,107 @@
+from hashlib import blake2s
+blake = lambda x: blake2s(x).digest()
+from py_ecc.optimized_bn128 import G1, G2, add, multiply, FQ, FQ2, pairing, \
+    normalize, field_modulus, b, b2, is_on_curve, curve_order
+
+def compress_G1(pt):
+    x, y = normalize(pt)
+    return x.n + 2**255 * (y.n % 2)
+
+def decompress_G1(p):
+    if p == 0:
+        return (FQ(1), FQ(1), FQ(0))
+    x = p % 2**255
+    y_mod_2 = p // 2**255
+    y = pow((x**3 + b.n) % field_modulus, (field_modulus+1)//4, field_modulus)
+    assert pow(y, 2, field_modulus) == (x**3 + b.n) % field_modulus
+    if y%2 != y_mod_2:
+        y = field_modulus - y
+    return (FQ(x), FQ(y), FQ(1))
+
+# 16th root of unity
+hex_root = FQ2([21573744529824266246521972077326577680729363968861965890554801909984373949499,
+                16854739155576650954933913186877292401521110422362946064090026408937773542853])
+
+assert hex_root ** 8 != FQ2([1,0])
+assert hex_root ** 16 == FQ2([1,0])
+
+def sqrt_fq2(x):
+    y = x ** ((field_modulus ** 2 + 15) // 32)
+    while y**2 != x:
+        y *= hex_root
+    return y
+
+def hash_to_G2(m):
+    k2 = m
+    while 1:
+        k1 = blake(k2)
+        k2 = blake(k1)
+        x1 = int.from_bytes(k1, 'big') % field_modulus
+        x2 = int.from_bytes(k2, 'big') % field_modulus
+        x = FQ2([x1, x2])
+        xcb = x**3 + b2
+        if xcb ** ((field_modulus ** 2 - 1) // 2) == FQ2([1,0]):
+            break
+    y = sqrt_fq2(xcb)
+    return multiply((x, y, FQ2([1,0])), 2*field_modulus-curve_order)
+
+def compress_G2(pt):
+    assert is_on_curve(pt, b2)
+    x, y = normalize(pt)
+    return (x.coeffs[0] + 2**255 * (y.coeffs[0] % 2), x.coeffs[1])
+
+def decompress_G2(p):
+    x1 = p[0] % 2**255
+    y1_mod_2 = p[0] // 2**255
+    x2 = p[1]
+    x = FQ2([x1, x2])
+    if x == FQ2([0, 0]):
+        return FQ2([1,0]), FQ2([1,0]), FQ2([0,0])
+    y = sqrt_fq2(x**3 + b2)
+    if y.coeffs[0] % 2 != y1_mod_2:
+        y = y * -1
+    assert is_on_curve((x, y, FQ2([1,0])), b2)
+    return x, y, FQ2([1,0])
+
+def sign(m, k):
+    return compress_G2(multiply(hash_to_G2(m), k))
+
+def privtopub(k):
+    return compress_G1(multiply(G1, k))
+
+def verify(m, pub, sig):
+    return pairing(decompress_G2(sig), G1) == pairing(hash_to_G2(m), decompress_G1(pub))
+
+def aggregate_sigs(sigs):
+    o = FQ2([1,0]), FQ2([1,0]), FQ2([0,0])
+    for s in sigs:
+        o = add(o, decompress_G2(s))
+    return compress_G2(o)
+
+def aggregate_pubs(pubs):
+    o = FQ(1), FQ(1), FQ(0)
+    for p in pubs:
+        o = add(o, decompress_G1(p))
+    return compress_G1(o)
+
+for x in (1, 5, 124, 735, 127409812145, 90768492698215092512159, 0):
+    print('Testing with privkey %d' % x)
+    p1 = multiply(G1, x)
+    p2 = multiply(G2, x)
+    msg = str(x).encode('utf-8')
+    msghash = hash_to_G2(msg)
+    assert normalize(decompress_G1(compress_G1(p1))) == normalize(p1)
+    assert normalize(decompress_G2(compress_G2(p2))) == normalize(p2)
+    assert normalize(decompress_G2(compress_G2(msghash))) == normalize(msghash)
+    sig = sign(msg, x)
+    pub = privtopub(x)
+    assert verify(msg, pub, sig)
+
+print('Testing signature aggregation')
+msg = b'cow'
+keys = [1, 5, 124, 735, 127409812145, 90768492698215092512159, 0]
+sigs = [sign(msg, k) for k in keys]
+pubs = [privtopub(k) for k in keys]
+aggsig = aggregate_sigs(sigs)
+aggpub = aggregate_pubs(pubs)
+assert verify(msg, aggpub, aggsig)
diff --git a/beacon_chain_impl/full_pos.py b/beacon_chain_impl/full_pos.py
new file mode 100644
index 0000000..992753d
--- /dev/null
+++ b/beacon_chain_impl/full_pos.py
@@ -0,0 +1,68 @@
+from hashlib import blake2s
+blake = lambda x: blake2s(x).digest()
+from ethereum.utils import normalize_address, hash32, trie_root, \
+    big_endian_int, address, int256, encode_hex, decode_hex, encode_int, \
+    big_endian_to_int
+from rlp.sedes import big_endian_int, Binary, binary, CountableList
+import rlp
+import bls
+import random
+
+class BeaconBlock(rlp.Serializable):
+    
+    fields = [
+        ('parent_hash', hash32),
+        ('skip_count', int256),
+        ('randao_reveal', hash32),
+        ('attestation_bitmask', binary),
+        ('attestation_aggregate_sig', int256),
+        ('ffg_signer_list', binary),
+        ('ffg_aggregate_sig', int256),
+        ('main_chain_ref', hash32),
+        ('state_hash', hash32),
+        ('height', int256),
+        ('sig', int256)
+    ]
+
+    def __init__(self,
+                 parent_hash=b'\x00'*32, skip_count=0, randao_reveal=b'\x00'*32,
+                 attestation_bitmask=b'', attestation_aggregate_sig=0,
+                 ffg_signer_list=b'', ffg_aggregate_sig=0, main_chain_ref=b'\x00'*32,
+                 state_hash=b'\x00'*32, height=0, sig=0):
+        # at the beginning of a method, locals() is a dict of all arguments
+        fields = {k: v for k, v in locals().items() if k != 'self'}
+        super(BlockHeader, self).__init__(**fields)
+
+def quick_sample(seed, validator_count, sample_count):
+    k = 0
+    while 256**k < n:
+        k += 1
+    o = []; source = seed; pos = 0
+    while len(o) < sample_count:
+        if pos + k > 32:
+            source = blake(source)
+            pos = 0
+        m = big_endian_to_int(source[pos:pos+k])
+        if n * (m // n + 1) <= 256**k:
+            o.append(m % n)
+        pos += k
+    return o
+
+privkeys = [int.from_bytes(blake2s(str(i).encode('utf-8'))) for i in range(3000)]
+
+def mock_make_child(parent_state, skips, ):
+    attest
+
+    fields = [
+        ('parent_hash', hash32),
+        ('skip_count', int256),
+        ('randao_reveal', hash32),
+        ('attestation_bitmask', binary),
+        ('attestation_aggregate_sig', int256),
+        ('ffg_signer_list', binary),
+        ('ffg_aggregate_sig', int256),
+        ('main_chain_ref', hash32),
+        ('state_hash', hash32),
+        ('height', int256),
+        ('sig', int256)
+    ]
diff --git a/clock_disparity/node.py b/clock_disparity/node.py
deleted file mode 100644
index 5ca4a7b..0000000
--- a/clock_disparity/node.py
+++ /dev/null
@@ -1,151 +0,0 @@
-import os
-from binascii import hexlify
-from Crypto.Hash import keccak
-import random
-
-def to_hex(s):
-    return hexlify(s).decode('utf-8')
-
-memo = {}
-
-def sha3(x):
-    if x not in memo:
-        memo[x] = keccak.new(digest_bits=256, data=x).digest()
-    return memo[x]
-
-def hash_to_int(h):
-    o = 0
-    for c in h:
-        o = (o << 8) + c
-    return o
-
-NOTARIES = 40
-BASE_TS_DIFF = 1
-SKIP_TS_DIFF = 6
-SAMPLE = 9
-MIN_SAMPLE = 5
-POWDIFF = 50 * NOTARIES
-SHARDS = 12
-
-def checkpow(work, nonce):
-    # Discrete log PoW, lolz
-    # Quadratic nonresidues only
-    return pow(work, nonce, 65537) * POWDIFF < 65537 * 2 and pow(nonce, 32768, 65537) == 65536
-
-class MainChainBlock():
-    def __init__(self, parent, pownonce, ts):
-        self.parent_hash = parent.hash if parent else (b'\x00' * 32)
-        assert isinstance(self.parent_hash, bytes)
-        self.hash = sha3(self.parent_hash + str(pownonce).encode('utf-8'))
-        self.ts = ts
-        if parent:
-            assert checkpow(parent.pownonce, pownonce)
-            assert self.ts >= parent.ts
-        self.pownonce = pownonce
-        self.number = 0 if parent is None else parent.number + 1
-            
-
-main_genesis = MainChainBlock(None, 59049, 0)
-
-class Node():
-
-    def __init__(self, _id, network, sleepy=False, careless=False, ts=0):
-        self.blocks = {
-            main_genesis.hash: main_genesis
-        }
-        self.main_chain = [main_genesis.hash]
-        self.timequeue = []
-        self.parentqueue = {}
-        self.children = {}
-        self.ts = ts
-        self.id = _id
-        self.network = network
-        self.used_parents = {}
-        self.processed = {}
-        self.sleepy = sleepy
-        self.careless = careless
-
-    def broadcast(self, x):
-        if self.sleepy and self.ts:
-            return
-        self.network.broadcast(self, x)
-        self.on_receive(x)
-
-    def log(self, words, lvl=3, all=False):
-        #if "Tick:" != words[:5] or self.id == 0:
-        if (self.id == 0 or all) and lvl >= 2:
-            print(self.id, words)
-
-    def on_receive(self, obj, reprocess=False):
-        if obj.hash in self.processed and not reprocess:
-            return
-        self.processed[obj.hash] = True
-        if isinstance(obj, MainChainBlock):
-            return self.on_receive_main_block(obj)
-
-    def add_to_timequeue(self, obj):
-        i = 0
-        while i < len(self.timequeue) and self.timequeue[i].ts < obj.ts: 
-            i += 1
-        self.timequeue.insert(i, obj)
-
-    def add_to_multiset(self, _set, k, v):
-        if k not in _set:
-            _set[k] = []
-        _set[k].append(v)
-
-    def change_head(self, chain, new_head):
-        chain.extend([None] * (new_head.number + 1 - len(chain)))
-        i, c = new_head.number, new_head.hash
-        while c != chain[i]:
-            chain[i] = c
-            c = self.blocks[c].parent_hash
-            i -= 1
-        for i in range(len(chain)):
-            assert self.blocks[chain[i]].number == i
-            assert self.blocks[chain[i]].ts <= self.ts
-
-    def process_children(self, h):
-        if h in self.parentqueue:
-            for b in self.parentqueue[h]:
-                self.on_receive(b, reprocess=True)
-            del self.parentqueue[h]
-
-    def on_receive_main_block(self, block):
-        # Parent not yet received
-        if block.parent_hash not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.parent_hash, block)
-            return None
-        if block.ts > self.ts:
-            self.add_to_timequeue(block)
-            return None
-        self.log("Processing main chain block %s" % to_hex(block.hash[:4]))
-        self.blocks[block.hash] = block
-        # Reorg the main chain if new head
-        if block.number > self.blocks[self.main_chain[-1]].number:
-            reorging = (block.parent_hash != self.main_chain[-1])
-            self.change_head(self.main_chain, block)
-        # Add child record
-        self.add_to_multiset(self.children, block.parent_hash, block.hash)
-        # Final steps
-        self.process_children(block.hash)
-        self.network.broadcast(self, block)
-
-    def is_descendant(self, a, b):
-        a, b = self.blocks[a], self.blocks[b]
-        while b.number > a.number:
-            b = self.blocks[b.parent_hash]
-        return a.hash == b.hash
-
-    def tick(self):
-        self.ts += 0.1
-        self.log("Tick: %.1f" % self.ts, lvl=1)
-        # Process time queue
-        while len(self.timequeue) and self.timequeue[0].ts <= self.ts:
-            self.on_receive(self.timequeue.pop(0))
-        # Attempt to mine a main chain block
-        pownonce = random.randrange(65537)
-        mchead = self.blocks[self.main_chain[-1]]
-        if checkpow(mchead.pownonce, pownonce):
-            assert self.ts >= mchead.ts
-            self.broadcast(MainChainBlock(mchead, pownonce, self.ts))
diff --git a/clock_disparity/test.py b/clock_disparity/test.py
index a942e9a..549c95e 100644
--- a/clock_disparity/test.py
+++ b/clock_disparity/test.py
@@ -1,16 +1,18 @@
 from networksim import NetworkSimulator
-from node import Node, NOTARIES, MainChainBlock, main_genesis
+from pos_node import Node, NOTARIES, Block, genesis
 from distributions import normal_distribution
 
 net = NetworkSimulator(latency=12)
-notaries = [Node(i, net, ts=max(normal_distribution(50, 50)(), 0)) for i in range(NOTARIES)]
+notaries = [Node(i, net, ts=max(normal_distribution(200, 200)(), 0) * 0.1, sleepy=i%4==0) for i in range(NOTARIES)]
 net.agents = notaries
 net.generate_peers()
-for i in range(4000):
+for i in range(100000):
     net.tick()
 for n in notaries:
+    print("Local timestamp: %.1f, timequeue len %d" % (n.ts, len(n.timequeue)))
     print("Main chain head: %d" % n.blocks[n.main_chain[-1]].number)
-    print("Total main chain blocks received: %d" % (len([b for b in n.blocks.values() if isinstance(b, MainChainBlock)]) - 1))
+    print("Total main chain blocks received: %d" % (len([b for b in n.blocks.values() if isinstance(b, Block)]) - 1))
+    print("Notarized main chain blocks received: %d" % (len([b for b in n.blocks.values() if isinstance(b, Block) and n.is_notarized(b)]) - 1))
 
 import matplotlib.pyplot as plt
 import networkx as nx
@@ -18,15 +20,22 @@ import random
 
 G=nx.Graph()
 
-#positions = {main_genesis.hash: 0, beacon_genesis.hash: 0}
+#positions = {genesis.hash: 0, beacon_genesis.hash: 0}
 #queue = [
 
 for b in n.blocks.values():
+    for en in notaries:
+        if isinstance(b, Block) and b.hash in en.processed and b.hash not in en.blocks:
+            assert (not en.have_ancestry(b.hash)) or b.ts > en.ts
     if b.number > 0:
-        if isinstance(b, MainChainBlock):
-            G.add_edge(b.hash, b.parent_hash, color='b')
+        if isinstance(b, Block):
+            if n.is_notarized(b):
+                G.add_edge(b.hash, b.parent_hash, color='b')
+            else:
+                G.add_edge(b.hash, b.parent_hash, color='#dddddd')
 
-cache = {main_genesis.hash: 0}
+
+cache = {genesis.hash: 0}
 
 def mkoffset(b):
     if b.hash not in cache:
diff --git a/sharding_fork_choice_poc/beacon_chain_node.py b/sharding_fork_choice_poc/beacon_chain_node.py
deleted file mode 100644
index 2860f2e..0000000
--- a/sharding_fork_choice_poc/beacon_chain_node.py
+++ /dev/null
@@ -1,363 +0,0 @@
-import os
-from binascii import hexlify
-from Crypto.Hash import keccak
-import random
-
-def to_hex(s):
-    return hexlify(s).decode('utf-8')
-
-memo = {}
-
-def sha3(x):
-    if x not in memo:
-        memo[x] = keccak.new(digest_bits=256, data=x).digest()
-    return memo[x]
-
-def hash_to_int(h):
-    o = 0
-    for c in h:
-        o = (o << 8) + c
-    return o
-
-NOTARIES = 40
-BASE_TS_DIFF = 1
-SKIP_TS_DIFF = 6
-SAMPLE = 9
-MIN_SAMPLE = 5
-POWDIFF = 50 * NOTARIES
-SHARDS = 12
-
-def checkpow(work, nonce):
-    # Discrete log PoW, lolz
-    # Quadratic nonresidues only
-    return pow(work, nonce, 65537) * POWDIFF < 65537 * 2 and pow(nonce, 32768, 65537) == 65536
-
-class MainChainBlock():
-    def __init__(self, parent, pownonce, ts):
-        self.parent_hash = parent.hash if parent else (b'\x00' * 32)
-        assert isinstance(self.parent_hash, bytes)
-        self.hash = sha3(self.parent_hash + str(pownonce).encode('utf-8'))
-        self.ts = ts
-        if parent:
-            assert checkpow(parent.pownonce, pownonce)
-            assert self.ts >= parent.ts
-        self.pownonce = pownonce
-        self.number = 0 if parent is None else parent.number + 1
-            
-
-# Not a full RANDAO; stub for now
-class BeaconBlock():
-    def __init__(self, parent, proposer, ts, sigs, main_chain_ref):
-        self.contents = os.urandom(32)
-        self.parent_hash = parent.hash if parent else (b'\x11' * 32)
-        self.hash = sha3(self.parent_hash + self.contents)
-        self.ts = ts
-        self.sigs = sigs
-        self.number = parent.number + 1 if parent else 0
-        self.main_chain_ref = main_chain_ref.hash if main_chain_ref else parent.main_chain_ref
-
-        if parent:
-            i = parent.child_proposers.index(proposer)
-            assert self.ts >= parent.ts + BASE_TS_DIFF + i * SKIP_TS_DIFF
-            assert len(sigs) >= parent.notary_req
-            for sig in sigs:
-                assert sig.target_hash == self.parent_hash
-
-        # Calculate child proposers
-        v = hash_to_int(sha3(self.contents))
-        self.child_proposers = []
-        while v > 0:
-            self.child_proposers.append(v % NOTARIES)
-            v //= NOTARIES
-
-        # Calculate notaries
-        first = parent and proposer == parent.child_proposers[0]
-        self.notary_req = 0 if first else MIN_SAMPLE
-        v = hash_to_int(sha3(self.contents + b':n'))
-        self.notaries = []
-        for i in range(SAMPLE if first else SAMPLE):
-            self.notaries.append(v % NOTARIES)
-            v //= NOTARIES
-
-        # Calculate shard proposers
-        v = hash_to_int(sha3(self.contents + b':s'))
-        self.shard_proposers = []
-        for i in range(SHARDS):
-            self.shard_proposers.append(v % NOTARIES)
-            v //= NOTARIES
-        
-
-class Sig():
-    def __init__(self, proposer, target):
-        self.proposer = proposer
-        self.target_hash = target.hash
-        self.hash = os.urandom(32)
-        assert self.proposer in target.notaries
-
-class ShardCollation():
-    def __init__(self, shard_id, parent, proposer, beacon_ref, ts):
-        self.proposer = proposer
-        self.parent_hash = parent.hash if parent else (bytes([40 + shard_id]) * 32)
-        self.hash = sha3(self.parent_hash + str(self.proposer).encode('utf-8') + beacon_ref.hash)
-        self.ts = ts
-        self.shard_id = shard_id
-        self.number = parent.number + 1 if parent else 0
-        self.beacon_ref = beacon_ref.hash
-
-        if parent:
-            assert self.shard_id == parent.shard_id
-            assert self.proposer == beacon_ref.shard_proposers[self.shard_id]
-            assert self.ts >= parent.ts
-
-        assert self.ts >= beacon_ref.ts
-
-main_genesis = MainChainBlock(None, 59049, 0)
-beacon_genesis = BeaconBlock(None, 1, 0, [], main_genesis)
-shard_geneses = [ShardCollation(i, None, 0, beacon_genesis, 0) for i in range(SHARDS)]
-
-class BlockMakingRequest():
-    def __init__(self, parent, ts):
-        self.parent = parent
-        self.ts = ts
-        self.hash = os.urandom(32)
-
-class Node():
-
-    def __init__(self, _id, network, sleepy=False, careless=False):
-        self.blocks = {
-            beacon_genesis.hash: beacon_genesis,
-            main_genesis.hash: main_genesis
-        }
-        for s in shard_geneses:
-            self.blocks[s.hash] = s
-        self.sigs = {}
-        self.beacon_chain = [beacon_genesis.hash]
-        self.main_chain = [main_genesis.hash]
-        self.shard_chains = [[g.hash] for g in shard_geneses]
-        self.timequeue = []
-        self.parentqueue = {}
-        self.children = {}
-        self.ts = 0
-        self.id = _id
-        self.network = network
-        self.used_parents = {}
-        self.processed = {}
-        self.sleepy = sleepy
-        self.careless = careless
-
-    def broadcast(self, x):
-        if self.sleepy and self.ts:
-            return
-        #self.log("Broadcasting %s %s" % ("block" if isinstance(x, BeaconBlock) else "sig", to_hex(x.hash[:4])))
-        self.network.broadcast(self, x)
-        self.on_receive(x)
-
-    def log(self, words, lvl=3, all=False):
-        #if "Tick:" != words[:5] or self.id == 0:
-        if (self.id == 0 or all) and lvl >= 2:
-            print(self.id, words)
-
-    def on_receive(self, obj, reprocess=False):
-        if obj.hash in self.processed and not reprocess:
-            return
-        self.processed[obj.hash] = True
-        #self.log("Processing %s %s" % ("block" if isinstance(obj, BeaconBlock) else "sig", to_hex(obj.hash[:4])))
-        if isinstance(obj, BeaconBlock):
-            return self.on_receive_beacon_block(obj)
-        elif isinstance(obj, MainChainBlock):
-            return self.on_receive_main_block(obj)
-        elif isinstance(obj, ShardCollation):
-            return self.on_receive_shard_collation(obj)
-        elif isinstance(obj, Sig):
-            return self.on_receive_sig(obj)
-        elif isinstance(obj, BlockMakingRequest):
-            if self.beacon_chain[-1] == obj.parent:
-                mc_ref = self.blocks[obj.parent]
-                for i in range(2):
-                    if mc_ref.number == 0:
-                        break
-                    #mc_ref = self.blocks[mc_ref].parent_hash
-                x = BeaconBlock(self.blocks[obj.parent], self.id, self.ts,
-                                self.sigs[obj.parent] if obj.parent in self.sigs else [],
-                                self.blocks[self.main_chain[-1]])
-                self.log("Broadcasting block %s" % to_hex(x.hash[:4]))
-                self.broadcast(x)
-
-    def add_to_timequeue(self, obj):
-        i = 0
-        while i < len(self.timequeue) and self.timequeue[i].ts < obj.ts: 
-            i += 1
-        self.timequeue.insert(i, obj)
-
-    def add_to_multiset(self, _set, k, v):
-        if k not in _set:
-            _set[k] = []
-        _set[k].append(v)
-
-    def change_head(self, chain, new_head):
-        chain.extend([None] * (new_head.number + 1 - len(chain)))
-        i, c = new_head.number, new_head.hash
-        while c != chain[i]:
-            chain[i] = c
-            c = self.blocks[c].parent_hash
-            i -= 1
-        for i in range(len(chain)):
-            assert self.blocks[chain[i]].number == i
-
-    def recalculate_head(self, chain, condition):
-        while not condition(self.blocks[chain[-1]]):
-            chain.pop()
-        descendant_queue = [chain[-1]]
-        new_head = chain[-1]
-        while len(descendant_queue):
-            first = descendant_queue.pop(0)
-            if first in self.children:
-                for c in self.children[first]:
-                    if condition(self.blocks[c]):
-                        descendant_queue.append(c)
-            if self.blocks[first].number > self.blocks[new_head].number:
-                new_head = first
-        self.change_head(chain, self.blocks[new_head])
-        for i in range(len(chain)):
-            assert condition(self.blocks[chain[i]])
-
-    def process_children(self, h):
-        if h in self.parentqueue:
-            for b in self.parentqueue[h]:
-                self.on_receive(b, reprocess=True)
-            del self.parentqueue[h]
-
-    def on_receive_main_block(self, block):
-        # Parent not yet received
-        if block.parent_hash not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.parent_hash, block)
-            return None
-        self.log("Processing main chain block %s" % to_hex(block.hash[:4]))
-        self.blocks[block.hash] = block
-        # Reorg the main chain if new head
-        if block.number > self.blocks[self.main_chain[-1]].number:
-            reorging = (block.parent_hash != self.main_chain[-1])
-            self.change_head(self.main_chain, block)
-            if reorging:
-                self.recalculate_head(self.beacon_chain,
-                    lambda b: isinstance(b, BeaconBlock) and b.main_chain_ref in self.main_chain)
-                for i in range(SHARDS):
-                    self.recalculate_head(self.shard_chains[i],
-                        lambda b: isinstance(b, ShardCollation) and b.shard_id == i and b.beacon_ref in self.beacon_chain)
-        # Add child record
-        self.add_to_multiset(self.children, block.parent_hash, block.hash)
-        # Final steps
-        self.process_children(block.hash)
-        self.network.broadcast(self, block)
-
-    def is_descendant(self, a, b):
-        a, b = self.blocks[a], self.blocks[b]
-        while b.number > a.number:
-            b = self.blocks[b.parent_hash]
-        return a.hash == b.hash
-
-    def change_beacon_head(self, new_head):
-        self.log("Changed beacon head: %s" % new_head.number)
-        reorging = (new_head.parent_hash != self.beacon_chain[-1])
-        self.change_head(self.beacon_chain, new_head)
-        if reorging:
-            for i in range(SHARDS):
-                self.recalculate_head(self.shard_chains[i],
-                    lambda b: isinstance(b, ShardCollation) and b.shard_id == i and b.beacon_ref in self.beacon_chain)
-        # Produce shard collations?
-        for s in range(SHARDS):
-            if self.id == new_head.shard_proposers[s]:
-                sc = ShardCollation(s, self.blocks[self.shard_chains[s][-1]], self.id, new_head, self.ts)
-                assert sc.beacon_ref == new_head.hash
-                assert self.is_descendant(self.blocks[sc.parent_hash].beacon_ref, new_head.hash)
-                self.broadcast(sc)
-            for c in self.shard_chains[s]:
-                assert self.blocks[c].shard_id == s and self.blocks[c].beacon_ref in self.beacon_chain
-
-    def on_receive_beacon_block(self, block):
-        # Parent not yet received
-        if block.parent_hash not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.parent_hash, block)
-            return
-        # Main chain parent not yet received
-        if block.main_chain_ref not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.main_chain_ref, block)
-            return
-        # Too early
-        if block.ts > self.ts:
-            self.add_to_timequeue(block)
-            return
-        # Check consistency of cross-link reference
-        assert self.is_descendant(self.blocks[block.parent_hash].main_chain_ref, block.main_chain_ref)
-        # Add the block
-        self.log("Processing beacon block %s" % to_hex(block.hash[:4]))
-        self.blocks[block.hash] = block
-        # Am I a notary, and is the block building on the head? Then broadcast a signature.
-        if block.parent_hash == self.beacon_chain[-1] or self.careless:
-            if self.id in block.notaries:
-                self.broadcast(Sig(self.id, block))
-        # Check for sigs, add to head?, make a block?
-        if len(self.sigs.get(block.hash, [])) >= block.notary_req:
-            if block.number > self.blocks[self.beacon_chain[-1]].number and block.main_chain_ref in self.main_chain:
-                self.change_beacon_head(block)
-            if self.id in self.blocks[block.hash].child_proposers:
-                my_index = self.blocks[block.hash].child_proposers.index(self.id)
-                target_ts = block.ts + BASE_TS_DIFF + my_index * SKIP_TS_DIFF
-                self.add_to_timequeue(BlockMakingRequest(block.hash, target_ts))
-        # Add child record
-        self.add_to_multiset(self.children, block.parent_hash, block.hash)
-        # Final steps
-        self.process_children(block.hash)
-        self.network.broadcast(self, block)
-
-    def on_receive_sig(self, sig):
-        self.add_to_multiset(self.sigs, sig.target_hash, sig)
-        # Add to head? Make a block?
-        if sig.target_hash in self.blocks and len(self.sigs[sig.target_hash]) == self.blocks[sig.target_hash].notary_req:
-            block = self.blocks[sig.target_hash]
-            if block.number > self.blocks[self.beacon_chain[-1]].number and block.main_chain_ref in self.main_chain:
-                self.change_beacon_head(block)
-            if self.id in block.child_proposers:
-                my_index = block.child_proposers.index(self.id)
-                target_ts = block.ts + BASE_TS_DIFF + my_index * SKIP_TS_DIFF
-                self.log("Making block request for %.1f" % target_ts)
-                self.add_to_timequeue(BlockMakingRequest(block.hash, target_ts))
-        # Rebroadcast
-        self.network.broadcast(self, sig)
-
-    def on_receive_shard_collation(self, block):
-        # Parent not yet received
-        if block.parent_hash not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.parent_hash, block)
-            return None
-        # Beacon ref not yet received
-        if block.beacon_ref not in self.blocks:
-            self.add_to_multiset(self.parentqueue, block.beacon_ref, block)
-            return None
-        # Check consistency of cross-link reference
-        assert self.is_descendant(self.blocks[block.parent_hash].beacon_ref, block.beacon_ref)
-        self.log("Processing shard collation %s" % to_hex(block.hash[:4]))
-        self.blocks[block.hash] = block
-        # Set head if needed
-        if block.number > self.blocks[self.shard_chains[block.shard_id][-1]].number and block.beacon_ref in self.beacon_chain:
-            self.change_head(self.shard_chains[block.shard_id], block)
-        # Add child record
-        self.add_to_multiset(self.children, block.parent_hash, block.hash)
-        # Final steps
-        self.process_children(block.hash)
-        self.network.broadcast(self, block)
-
-    def tick(self):
-        if self.ts == 0:
-            if self.id in beacon_genesis.notaries:
-                self.broadcast(Sig(self.id, beacon_genesis))
-        self.ts += 0.1
-        self.log("Tick: %.1f" % self.ts, lvl=1)
-        # Process time queue
-        while len(self.timequeue) and self.timequeue[0].ts <= self.ts:
-            self.on_receive(self.timequeue.pop(0))
-        # Attempt to mine a main chain block
-        pownonce = random.randrange(65537)
-        mchead = self.blocks[self.main_chain[-1]]
-        if checkpow(mchead.pownonce, pownonce):
-            self.broadcast(MainChainBlock(mchead, pownonce, self.ts))