Explicit reference: ![alt text][img1] in paragraph.
Implicit reference: ![Logo][] shows brand.
Shortcut reference: ![Icon] works too.
Multiple images: ![first][i1] and ![second][i2] together.
Unresolved: ![missing][nonexistent] stays as-is.
Case insensitive: ![ALT][myimg] matches lowercase definition.
Complex alt: ![**bold** and `code`][img1] with formatting.