diff --git a/cryptarchia/cryptarchia.py b/cryptarchia/cryptarchia.py
new file mode 100644
index 0000000..296e311
--- /dev/null
+++ b/cryptarchia/cryptarchia.py
@@ -0,0 +1,154 @@
+
+
+# Please note this is still a work in progress
+from dataclasses import dataclass
+
+Id: TypeAlias = bytes
+
+@dataclass
+class Epoch:
+    # identifier of the epoch, counting incrementally from 0
+    epoch: int
+
+# An absolute unique indentifier of a slot, counting incrementally from 0
+@dataclass
+class Slot:
+    absolute_slot: int
+
+    def from_unix_timestamp_s(config: TimeConfig, timestamp_s: int) -> Date:
+        absolute_slot = timestamp_s // config.slot_duration
+        return Slot(absolute_slot)
+
+    def epoch(self, config: TimeConfig) -> Epoch:
+        return self.absolute_slot // config.slots_per_epoch
+
+
+@dataclass
+class TimeConfig:
+    # How many slots in a epoch, all epochs will have the same number of slots
+    slots_per_epoch: int
+    # How long a slot lasts in seconds
+    slot_duration: int
+    # Start of the first epoch, in unix timestamp second precision
+    chain_start_time: int
+
+
+@dataclass 
+class Config:
+    k: int
+    time: TimeConfig
+
+@dataclass
+class BlockHeader:
+    slot: Slot
+    parent: Id
+    _id: Id  # this is an abstration over the block id
+
+    def parent(self) -> Id:
+        return self.parent
+
+    def id(self) -> Id:
+        return self._id
+
+
+@dataclass 
+class Chain:
+    blocks: List[BlockHeader]
+
+    def tip(self) -> BlockHeader:
+        return self.blocks[-1]
+
+    def length(self) -> int:
+        return len(self.blocks)
+
+    def contains_block(self, block: BlockHeader) -> bool:
+        return block in self.blocks
+    
+    def block_position(self, block: BlockHeader) -> int:
+        assert self.contains_block(block)
+        for (i, b) in enumerate(self.blocks):
+            if b == block:
+                return i
+
+class Follower:
+    def __init__(self, genesis: BlockHeader, config: Config):
+        self.config = config
+        self.forks = []
+        self.local_chain = Chain([genesis])
+
+    # We don't do any validation in the current version
+    def validate_header(block: BlockHeader) -> bool:
+        True
+
+    # Try appending this block to an existing chain and return whether
+    # the operation was successful
+    def try_extend_chains(self, block: BlockHeader) -> bool:
+        if self.local_chain.tip().id() == block.parent():
+            self.local_chain.blocks.append(block)
+            return True
+        
+        for chain in self.forks:
+            if chain.tip().id() == block.parent():
+                chain.blocks.append(block)
+                return True
+
+        return False
+
+
+    def try_create_fork(self, block: BlockHeader) -> Option[Chain]:
+        chains = self.forks + [self.local_chain]
+        for chain in chains:
+            if self.chain.contains_block(block):
+                block_position = chain.block_position(block)
+                return Chain(blocks = chain.blocks[:block_position] + [block])
+        
+        return None
+
+    def on_block(self, block: BlockHeader):
+        if not self.validate_header(block):
+            return
+
+        # check if the new block extends an existing chain
+        if self.try_extend_chains(block):
+            return
+
+        # if we get here, we might need to create a fork
+        new_chain = self.try_create_fork(block)
+        if new_chain is not None:
+            self.forks.append(new_chain)
+        # otherwise, we're missing the parent block
+        # in that case, just ignore the block
+        
+
+    # Evaluate the fork choice rule and return the block header of the block that should be the head of the chain
+    def fork_choice(local_chain: Chain, forks: List[Chain]) -> BlockHeader:
+        pass
+        
+
+    def tip(self) -> BlockHeader:
+        return self.fork_choice()
+
+
+@dataclass
+class Coin:
+    value: int
+
+class Leader:
+    def init(self, genesis: BlockHeader, config: TimeConfig, coins: List[Coin]):
+        self.config = config
+        self.tip = genesis
+        self.coins = coins
+
+    def is_leader_at(self, slot: Slot) -> bool:
+        for coin in self.coins:
+            if lottery(slot, coin):
+                return True
+        return False
+    
+    def propose_block(self, slot: Slot, parent: BlockHeader) -> BlockHeader:
+        assert self.is_leader_at(slot)
+        return BlockHeader(parent=parent.id(), slot=slot, _id=Id(b"TODO"))
+
+
+if __name__ == "__main__":
+    pass
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