UX challenges

Multiple balances (L1 + L2)

Possible solutions

• Only do layer 1
• Show both balances (savings / spending account)
• Keep money in one layer only --> swap

Receiving on both layers

Possible solutions

• Only allow receiving on one layer
• Let user switch between layers
• Propose sensible layer for given amount
• Use L1-fallback-address in L2-invoice

Sending to both layers

Possible solutions

• Only allow sending to one layer
• Close/open a channel (on-the-fly)
• Use swaps

Edge case: Payee displays both options. How should we pay?

L1: Payment is stuck

• Payment cannot be canceled
• Is payment still in mempool?
• Bump fee

LN: Channel reserves

Channel has a reserve of 1% of the total capacity

User cannot send full balance!

Never display that amount as being owned?

Channel reserves may change.

Solution: Abolish channel reserves on user side?

LN: Multiple channels

User has 3 channels with 1'000 sats outbound-capacity each.

Wants to pay 2'500 sats

Solution: MPP (Multi-path-payments)

On-boarding process

• Install Lightning app
• Send on-chain funds to Lightning app
• Open Lightning channel
• Spend / swap out sats
• I can finally receive (some) sats :-)
• Solution: LSP

Lightning Service Provider

• Pioneered by Breez
• Open channel to newly installed wallet
• Even better: Open channel on-the-fly
• Explain fee situation! (--> Spontaneous payments?)

Channel opening cost

• Lightning network fee
• On-chain fee channel opening
• Estimated on-chain fee for channel closing
• Estimated on-chain fees for consolidating UTXOs
• Channel reserves (?)

Spontaneous payments

• Mobile is not online
• User needs to open wallet to pull his funds
• What if user doesn't open app?
• On-chain fallback? Dust payment?