diff --git a/shared/mainnet/config.yaml b/shared/mainnet/config.yaml
index d4c7a46..9ec2df7 100644
--- a/shared/mainnet/config.yaml
+++ b/shared/mainnet/config.yaml
@@ -1,156 +1,77 @@
-# Mainnet preset
+# Mainnet config
 
-CONFIG_NAME: "mainnet"
+# Extends the mainnet preset
+PRESET_BASE: 'mainnet'
 
-# Misc
+# Transition
+# ---------------------------------------------------------------
+# TBD, 2**256-2**10 is a placeholder
+TERMINAL_TOTAL_DIFFICULTY: 115792089237316195423570985008687907853269984665640564039457584007913129638912
+# By default, don't use this param
+TERMINAL_BLOCK_HASH: 0x0000000000000000000000000000000000000000000000000000000000000000
+
+
+# Genesis
 # ---------------------------------------------------------------
-# 2**6 (= 64)
-MAX_COMMITTEES_PER_SLOT: 64
-# 2**7 (= 128)
-TARGET_COMMITTEE_SIZE: 128
-# 2**11 (= 2,048)
-MAX_VALIDATORS_PER_COMMITTEE: 2048
-# 2**2 (= 4)
-MIN_PER_EPOCH_CHURN_LIMIT: 4
-# 2**16 (= 65,536)
-CHURN_LIMIT_QUOTIENT: 65536
-# See issue 563
-SHUFFLE_ROUND_COUNT: 90
 # `2**14` (= 16,384)
 MIN_GENESIS_ACTIVE_VALIDATOR_COUNT: 16384
 # Dec 1, 2020, 12pm UTC
 MIN_GENESIS_TIME: 1606824000
-# 4
-HYSTERESIS_QUOTIENT: 4
-# 1 (minus 0.25)
-HYSTERESIS_DOWNWARD_MULTIPLIER: 1
-# 5 (plus 1.25)
-HYSTERESIS_UPWARD_MULTIPLIER: 5
-
-
-# Fork Choice
-# ---------------------------------------------------------------
-# 2**3 (= 8)
-SAFE_SLOTS_TO_UPDATE_JUSTIFIED: 8
-
-
-# Validator
-# ---------------------------------------------------------------
-# 2**11 (= 2,048)
-ETH1_FOLLOW_DISTANCE: 2048
-# 2**4 (= 16)
-TARGET_AGGREGATORS_PER_COMMITTEE: 16
-# 2**0 (= 1)
-RANDOM_SUBNETS_PER_VALIDATOR: 1
-# 2**8 (= 256)
-EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION: 256
-# 14 (estimate from Eth1 mainnet)
-SECONDS_PER_ETH1_BLOCK: 14
-
-
-# Deposit contract
-# ---------------------------------------------------------------
-# Ethereum PoW Mainnet
-DEPOSIT_CHAIN_ID: 1
-DEPOSIT_NETWORK_ID: 1
-# **TBD**
-DEPOSIT_CONTRACT_ADDRESS: 0x00000000219ab540356cBB839Cbe05303d7705Fa
+# Mainnet initial fork version, recommend altering for testnets
+GENESIS_FORK_VERSION: 0x00000000
+# 604800 seconds (7 days)
+GENESIS_DELAY: 604800
 
 
-# Gwei values
+# Forking
 # ---------------------------------------------------------------
-# 2**0 * 10**9 (= 1,000,000,000) Gwei
-MIN_DEPOSIT_AMOUNT: 1000000000
-# 2**5 * 10**9 (= 32,000,000,000) Gwei
-MAX_EFFECTIVE_BALANCE: 32000000000
-# 2**4 * 10**9 (= 16,000,000,000) Gwei
-EJECTION_BALANCE: 16000000000
-# 2**0 * 10**9 (= 1,000,000,000) Gwei
-EFFECTIVE_BALANCE_INCREMENT: 1000000000
-
+# Some forks are disabled for now:
+#  - These may be re-assigned to another fork-version later
+#  - Temporarily set to max uint64 value: 2**64 - 1
 
-# Initial values
-# ---------------------------------------------------------------
-# Mainnet initial fork version, recommend altering for testnets
-GENESIS_FORK_VERSION: 0x00000000
-BLS_WITHDRAWAL_PREFIX: 0x00
+# Altair
+ALTAIR_FORK_VERSION: 0x01000000
+ALTAIR_FORK_EPOCH: 74240  # Oct 27, 2021, 10:56:23am UTC
+# Merge
+MERGE_FORK_VERSION: 0x02000000
+MERGE_FORK_EPOCH: 18446744073709551615
+# Sharding
+SHARDING_FORK_VERSION: 0x03000000
+SHARDING_FORK_EPOCH: 18446744073709551615
 
 
 # Time parameters
 # ---------------------------------------------------------------
-# 604800 seconds (7 days)
-GENESIS_DELAY: 604800
 # 12 seconds
 SECONDS_PER_SLOT: 12
-# 2**0 (= 1) slots 12 seconds
-MIN_ATTESTATION_INCLUSION_DELAY: 1
-# 2**5 (= 32) slots 6.4 minutes
-SLOTS_PER_EPOCH: 32
-# 2**0 (= 1) epochs 6.4 minutes
-MIN_SEED_LOOKAHEAD: 1
-# 2**2 (= 4) epochs 25.6 minutes
-MAX_SEED_LOOKAHEAD: 4
-# 2**6 (= 64) epochs ~6.8 hours
-EPOCHS_PER_ETH1_VOTING_PERIOD: 64
-# 2**13 (= 8,192) slots ~13 hours
-SLOTS_PER_HISTORICAL_ROOT: 8192
+# 14 (estimate from Eth1 mainnet)
+SECONDS_PER_ETH1_BLOCK: 14
 # 2**8 (= 256) epochs ~27 hours
 MIN_VALIDATOR_WITHDRAWABILITY_DELAY: 256
 # 2**8 (= 256) epochs ~27 hours
 SHARD_COMMITTEE_PERIOD: 256
-# 2**2 (= 4) epochs 25.6 minutes
-MIN_EPOCHS_TO_INACTIVITY_PENALTY: 4
-
-
-# State vector lengths
-# ---------------------------------------------------------------
-# 2**16 (= 65,536) epochs ~0.8 years
-EPOCHS_PER_HISTORICAL_VECTOR: 65536
-# 2**13 (= 8,192) epochs ~36 days
-EPOCHS_PER_SLASHINGS_VECTOR: 8192
-# 2**24 (= 16,777,216) historical roots, ~26,131 years
-HISTORICAL_ROOTS_LIMIT: 16777216
-# 2**40 (= 1,099,511,627,776) validator spots
-VALIDATOR_REGISTRY_LIMIT: 1099511627776
-
-
-# Reward and penalty quotients
-# ---------------------------------------------------------------
-# 2**6 (= 64)
-BASE_REWARD_FACTOR: 64
-# 2**9 (= 512)
-WHISTLEBLOWER_REWARD_QUOTIENT: 512
-# 2**3 (= 8)
-PROPOSER_REWARD_QUOTIENT: 8
-# 2**26 (= 67,108,864)
-INACTIVITY_PENALTY_QUOTIENT: 67108864
-# 2**7 (= 128) (lower safety margin at Phase 0 genesis)
-MIN_SLASHING_PENALTY_QUOTIENT: 128
-# 1 (lower safety margin at Phase 0 genesis)
-PROPORTIONAL_SLASHING_MULTIPLIER: 1
+# 2**11 (= 2,048) Eth1 blocks ~8 hours
+ETH1_FOLLOW_DISTANCE: 2048
 
 
-# Max operations per block
+# Validator cycle
 # ---------------------------------------------------------------
+# 2**2 (= 4)
+INACTIVITY_SCORE_BIAS: 4
 # 2**4 (= 16)
-MAX_PROPOSER_SLASHINGS: 16
-# 2**1 (= 2)
-MAX_ATTESTER_SLASHINGS: 2
-# 2**7 (= 128)
-MAX_ATTESTATIONS: 128
-# 2**4 (= 16)
-MAX_DEPOSITS: 16
-# 2**4 (= 16)
-MAX_VOLUNTARY_EXITS: 16
+INACTIVITY_SCORE_RECOVERY_RATE: 16
+# 2**4 * 10**9 (= 16,000,000,000) Gwei
+EJECTION_BALANCE: 16000000000
+# 2**2 (= 4)
+MIN_PER_EPOCH_CHURN_LIMIT: 4
+# 2**16 (= 65,536)
+CHURN_LIMIT_QUOTIENT: 65536
 
 
-# Signature domains
+# Deposit contract
 # ---------------------------------------------------------------
-DOMAIN_BEACON_PROPOSER: 0x00000000
-DOMAIN_BEACON_ATTESTER: 0x01000000
-DOMAIN_RANDAO: 0x02000000
-DOMAIN_DEPOSIT: 0x03000000
-DOMAIN_VOLUNTARY_EXIT: 0x04000000
-DOMAIN_SELECTION_PROOF: 0x05000000
-DOMAIN_AGGREGATE_AND_PROOF: 0x06000000
+# Ethereum PoW Mainnet
+DEPOSIT_CHAIN_ID: 1
+DEPOSIT_NETWORK_ID: 1
+DEPOSIT_CONTRACT_ADDRESS: 0x00000000219ab540356cBB839Cbe05303d7705Fa