Gamplay with 16-bit Scaled Integer Physics

The gameplay for Troll Mountain Taxi is coming together.

Joystick controls up / left / right accelerate the balloon and gravity drags it back down.

I used scaled 16-bit integers for the physics. 1 bit sign, 9 bits pixel position, 6 bits fractional pixels: 

S 8 7 6 5 4 3 2     1 0 F F F F F F

When positioning sprites, bit 8 goes into the high bit of X position, then a bit of shifting to get bits 0 and 1 into the high byte to populate the low byte of the X position.

My Son did the music arrangement, based on Hall of the Mountain King. Two channels, so as to leave a channel for sound effects. I had to enhance my music player to support patches, as the tune has >256 notes.

Collision detection is working but I haven't implemented the crashing yet. The balloon just turns red.

When the crashes are done, I'll probably release the PRG file and see if anyone would like to play with the controls.

I fell into a few traps with the scaled integers and sprite positions. I kind of wish I'd done a simpler game with sprites first! :)