In the emulator

With openMSX and the Philips_VG_8020 machine:

echo 3 > work/fase.txt
openmsx -machine Philips_VG_8020 -cart magicaltree.rom -script tools/omsx_fases.tcl

tools/omsx_fases.tcl:

• reads the stage from work/fase.txt (0 to 8) and writes it into 0xE05C, 0xE05D and 0xE051 at 0x51D2, before the graphics are set up;
• dumps RAM and VRAM on the first game frame (0x4184), which is step 26;
• climbs the stage without playing it: stopped on the jr $ at 0x40A5, it runs 0x6749 thirty times from a piece of code at 0xE800, with the hook replaced by a ret so that the game frame does not draw in between;
• dumps every thirty steps, up to the end of the stage, into work/fases/.

The whole game happens in the hook at 0x402C: a breakpoint there stops once per frame.

A warning: if a breakpoint's command fails, openMSX freezes the emulation. The script wraps its commands in catch and logs the error in work/fases/log.txt.