WoW.. Very VERY impressive. I also realy like the Zanac-music tribute! 
I think I'll have to get out my joystick and spend some time with this game. Impressive to see what can be done on a humble MSX1. Also really like the use of colors on the sprites!
Only one small thing: Maybe a bigger explosion after killing the level 1 end boss would be nice?
But still... I can't wait untill I can play this game!
@Grauw actually I set a number of transiction frames to accelerate. Actually, during acceleration, the scroll does 20 rows at 2 pixels, 20 at 4 pixel speed and then 8 pixel speed until the map is ended, after the boss is dead. I can set a big number. it was set at actual value long time ago, when I've implemented acceleration. I used the value "20" because when I did it the damage inflicted by weapon wasn't like actual and often I was able to kill the boss before the acceleration could reach the max speed (so it seemed unuseful). But yes, I can change this value now 
@Manuel probably in a new project XD actually the code is almost complete and I have really few remaining bytes. I want to see a complete project so if I keep adding stuff it will never end. The last thing I'll add will be the 2nd secret (1st is the above mentioned music test and 3rd is the cheats activation and both are already implemented). The time left until msxdev deadline will be used to draw gfx, sprites and bosses, do the tilemaps and coding for bosses movement and collisions (yep all of them have own, but you'll se by yourself in a few days) for level 4 and 5. And then I plan to add prologue and epilogue sequences, so other gfx, and new musics. I think it will be done AFTER msxdev (but I'll do, I SWEAR) and actually I don't know how many room they will need. But I can add some pages thanks to ASCII16 mapper... we'll see.
@Grauw actually I set a number of transiction frames to accelerate. Actually, during acceleration, the scroll does 20 rows at 2 pixels, 20 at 4 pixel speed and then 8 pixel speed until the map is ended, after the boss is dead. I can set a big number. it was set at actual value long time ago, when I've implemented acceleration. I used the value "20" because when I did it the damage inflicted by weapon wasn't like actual and often I was able to kill the boss before the acceleration could reach the max speed (so it seemed unuseful). But yes, I can change this value now
I mean to increase not in whole pixel steps, but to also have a “1.5” speed during the acceleration where it goes between 1 and 2 steps each frame for a while. During a constant scroll speed this won’t look nice, it will look jerky, but during a linear acceleration it will look good I think as long as you always end the transition at a whole number.
Currently you probably have an “y” variable which is an 8-bit value, the lowest 3 bits determine the character offset and the upper 5 bits the character scroll position. If you add another byte to the “y” variable to act as a fraction (a fixed-point number), and instead of adding e.g. 1 or 2 you add 100H or 200H, or indeed, 180H (1.5), you can have scroll speeds with a fraction. You only use the upper byte for the actual “y” position, the lower byte will accumulate based on the step size and make the upper byte increase by 1 1 1 2 1 1 1 2 if you use increment 1.40H, 1 2 1 2 1 2 1 2 if you use increment 1.80H, etc.