Yeah, the web version is weird, I wouldn't recommend it. When I added it to the page it was like 5~10min before the deadline so I couldn't really fix it, I haven't got much experience in that.
About the gameplay, it's 2 coins = 1 life and 1 damage = -1 life. Touching the mailbox trigger the night, which changes what you have collected on your way to it.
About level 2, you need to just not pick up the second coin on the top row :) also, can't touch the spike.