Looking at a computer screen, which showed various images of grass at different vividnesses to give examples of differences of vividness in lucid dreams.
How did I not become lucid...

I was up on a grassy mountain, looking at these roller coasters. Two people were talking about them behind me. Then I was cycling on a mountain bike around this mountain, and the two people were cheering me on. The Clash song "Lost in the Supermarket" was playing, and as the line "I kick some holes in the pipes in the wall" came, I saw a pipe and kicked it. Then I was riding backwards, and fearing a crash.