Sonic 1-squared

Sonic 1-squared is an enhanced version of the original Sonic the Hedgehog game engine. Various changes are planned to make editing the game easier.

Features

• The player's Chaos Emerald count is stored as a bitfield instead of a list. It's a longword, so there can be up to 32 Emeralds.
• LoadPerZone subroutine consolidates all pointers and parameters for zones and acts. This simplifies the process of adding levels. (incomplete)
• LoadPerCharacter subroutine does the same for the Sonic object, palette and life icon, allowing for extra characters.
• LoadPerDemo loads the level number, demo data, character and start position for all demos, including those during the credits.
• Rewritten level select routine to be more customisable. It now uses standard ASCII, and supports multiple columns (which are automatically generated based on the lines-per-column setting).
• The hidden Japanese credits, "try again" and "end" screens have been given their own gamemodes, which are accessible through the level select.
• The HUD has new debug features, including a CPU cycle usage counter (displayed as a decimal percentage) and sprite counter ($4F is max).
• 6 button support. v_joypad_hold_actual_xyz contains the status of the X/Y/Z/Mode buttons.

Graphics

• KosPLC subroutine loads Kosinski-compressed graphics at the beginning of a level.
• UncPLC subroutine load uncompressed graphics at any time. This complements KosPLC by loading graphics during a level. Both this and KosPLC use the DMA queue.
• DMA queue system for loading uncompressed graphics.
• Animated level graphics use a script instead of being hard-coded. The exception is Marble Zone's magma, which works somewhat differently to other animations.
• Palette cycling uses a script.
• Water palettes are generated in-game by the WaterFilter subroutine, instead of being hardcoded.
• Fading to black/white is controlled by a brightness variable, and no longer requires a "next" palette. This simplifies loading new palettes.

Objects

• Modified the way animation works to save 2 bytes in RAM per object. The high bit of ost_anim now serves as an update flag instead of ost_anim_restart.
• Object scratch RAM is assigned automatically with rsobj macro. If you attempt to use more RAM than is available ($40 bytes), assembly will fail.
• ost_id is now a longword pointer instead of a single byte (as is the case in Sonic 3 & Knuckles). This allows for unlimited object types, and slightly improves performance.
• ost_frame extended to a word (ost_frame_hi), allowing objects to have up to 8,192 distinct frames of animation.
• Sprite mappings use 6 bytes per piece instead of 5, and the piece count is a word instead of a byte. This ensures the data is always aligned to even.
• ost_parent contains the parent object's OST address (shortened to a word), if SaveParent was called when the child object was created. GetParent will set the parent object as a1. Calling DeleteFamily will delete an object as well as any objects which have it set as their parent.
• ost_linked is similar to ost_parent. GetLinked will set the linked object as a1. DeleteFamily won't delete linked objects.
• Monitor icons load only as needed, allowing for up to 256 unique monitor types (with a maximum of 8 loaded at any one time).
• Each title card has its own PLC, so only letters that are used need to be loaded. Title cards are automatically centered by the autocard macro. Title card mappings are also automated, and can use sprite mappings more efficiently by joining two letters together as a single sprite.
• GHZ/SLZ loops use an object instead of being hard-coded. The object reads Sonic's position within the loop and updates the level layout accordingly.
• Debug mode has been rewritten with more features, including info overlays for Sonic and the nearest object (similar to those in the Sonic Physics Guide). The controls are as follows:
  • B - Toggle between Sonic and object.
  • C (as object) - Place an object.
  • Hold A (as object) - Select an object with left/right. The previous and next objects are now visible.
  • X - Target overlay to current nearest object. This is not automatically updated until the targeted object despawns.
  • Y - Toggle between displaying x/y position, x/y speed, angle/routine numbers and nothing.
  • Z - Toggle between displaying actual width/height, hitbox width/height and nothing.

Bugfixes

• Spikes no longer kill Sonic immediately after losing rings. Add $80 to the subtype to restore the original lethal behaviour.

Credits

• flamewing for mdcomp.
• vladikcomper for the advanced error handler.
• Devon for the optimised CalcAngle routine.