An original character · A source-based movement study
Meet Copper, our tenrec test character. Run, roll and jump through the original Green Hill Act 1 terrain while we study its movement and camera.
Arrow keys to move · Space to jump
Down to roll · Up to look
USB / Bluetooth controller
Press a button on your controller
Connect it, click the game, then press a controller button. D-pad or left stick moves; face buttons jump; Start pauses or resumes.
Input: At rest
For an unfamiliar HID layout, choose Map controls and follow the prompts. Mappings stay in this browser.
Why the screen moves
Inside that horizontal band, the camera waits. Move past it and the scenery scrolls while Copper stays near the same place on screen. Vertical movement has a wider airborne window. The distant scenery scrolls at different speeds, just as the REV00 routines specify.
Yellow: camera window Cyan: body collision box Pink: terrain sensor
What this build proves
The player uses the original fixed-point constants, terrain profiles and movement order. Six movement sequences, including a loop, matched the original ROM across 880 updates and 11,440 compared fields. That verifies those sequences; it does not establish a complete game reconstruction.
Some objects, activation rules, terrain animation and game events remain incomplete. This course uses original reference art. Copper’s artwork is newly generated. Our own stage comes next.
Character study / 24 poses
Idle, walk, run, jump, roll, brake, look, crouch, hurt and balance. The runtime manifest supplies individual crops and pivots for consistent feet and body placement.
Download the transparent sheet ↗ Frame manifest ↗
A separate experiment
The original Sonic first stage is being reconstructed in editable Java, with the same lighting and weather presentation.
Open the Java first stage →Development notes