"bet on even/odd, 1-18/19-36 or red/black, and zero comes in, the house takes half your stake only."

That's the La Partage rule, similar to a surrender option in some casinos on blackjack tables.

Depending on the casino, En Prison can be like La Partage, where you lose half your bet on an even money wager when zero hits. But, En Prison usually means your even money bet (the whole amount) stays where it is when a zero hits. The bet is still live for the next spin. If zero hits on the next spin, you lose the entire bet. This rule (and also La Partage) reduces the house odds to 1.35%. This was how they ran the French wheel at the Paris.

God I miss that table!