Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
This block will teleport you to another level (set in the .asm file) after you collected 8 (customizable) of it. They shatter when you touch them. Uses one byte of empty RAM - this address can be altered easily and has to be in the 16-bit range ($0000-$1FFF).