What dos it mean when a guy flashes his abs at you?

there's this guy I like that I think likes me back. He spilled something on his sweatshirt then he took a step toward me and he lifted his sweatshirt showing his stomach to me? I don't know what that means at all an I'm pretty sure he was intentionally doing that since he was facing me. He was flirting with me a few seconds before.
What dos it mean when a guy flashes his abs at you?
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