Add Special Stages

[luksamuk]

Special Stage design

The special stage will be in full 3D (target is 30 FPS), being a prism tube with three lanes. The tube will not control like Sonic 2's half pipes; instead, it will be somewhat inspired by the endless runner genre.

For ease of design, the prism tube can be built out of smaller terrain models rendered as needed. We don't have to render anything behind the player, and terrain parts could be recycled.

The tube's visuals will explore transparency and perharps reflection, since these features are somewhat limited on the Sega Saturn: we'll strive for something that seems like "the PlayStation 1 differential" here.

Background is going to be full of stars and aurora borealis.

Sonic will be able to collect orbs and rings and may receive a penalty when hitting crystal shards that are spawned on the way. Rings will act as health (perharps carry on rings from the previous stage).

Technical discussion and preparation

Since these stages are completely made in 3D, we need to be able to encode Sonic's model, rigging and animations and play them in a very simple manner. This also implies studying Blender so we can properly export low-poly polygons to custom formats.

See sub-issues for more information!