Interactive N64 RDP triangle demo

Changes:

• Flip triangle horizontally with B button
• Initial triangle now centered
• Avoid crashes in line drawing functions when moving out of visible area
• Other small fixes

Controls and usage:

Btn	Action
L	Switch to previous variable
R	Switch to next variable
D ◀︎	Decrease current variable
D ▶︎	Increase current variable
A	Invert left/right major
B	Flip triangle horizontally

The variables are cycled in the order YL, YM, YH, XL, XM, XH, DxLDy, DxMDy, DxHDy.
The slope variables (DxLDy, DxMDy and DxHDy) change by steps of 0.125 while the positional variables change by steps of 1.

Interactive N64 RDP triangle demo

Controls:

L/R = select variable to change
D-pad left/right = change value of variable
A = switch left/right major

Triangle demo

Controls:

L/R = select variable to change
D-pad left/right = change value of variable
A = switch left/right major