TRACE · ROUND 3

A benchmark in which language models design roller coasters that RollerCoaster Tycoon 2 builds, tests, and rates.

claude-opus-5 · 20260725-opus5-blind · round 3 back to model →
events
40
tool calls
35
rejected
2
session
0:00
Session trace

  1. I'll start by loading the coaster tools.

  2. ToolSearch
    {"max_results":20,"query":"coaster ride track piece"}
  3. piece_geometry
    {"dir":0}
    {"deltas":[{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"flat","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"end_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"begin_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"middle_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":16,"piece":"up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":64,"piece":"up_60","slope_out":4},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":8,"piece":"flat_to_up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":32,"piece":"up_25_to_up_60","slope_out":4},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":32,"piece":"up_60_to_up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":8,"piece":"up_25_to_flat","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":-16,"piece":"down_25","slope_out":6},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":-64,"piece":"down_60","slope_out":8},{"bank_out":0,"dir_out":0,"dx… (7397 chars)
  4. new_ride
    {"dir":0,"ride_type":51,"x":62,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"ride_id":0}
  5. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60","down_60_to_down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":32,"y":50,"z":112},"placed_this_call":30,"total_placed":30}
  6. place_pieces
    {"pieces":["flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":23,"y":46,"z":112},"placed_this_call":11,"total_placed":41}
  7. place_pieces
    {"pieces":["flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":33,"y":45,"z":112},"placed_this_call":9,"total_placed":50}
  8. place_pieces
    {"pieces":["flat_to_up_25","up_25_to_flat","half_loop_up","half_loop_down","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":35,"y":45,"z":128},"placed_this_call":2,"rejection":{"error":"piece enters at 25-up slope but the track here is flat; add a slope transition piece first","index":2,"piece":"half_loop_up"},"total_placed":52}
  9. undo_piece
    {"cursor":{"bank":0,"dir":2,"slope":2,"x":34,"y":45,"z":120},"pieces_placed":51,"removed":"up_25_to_flat"}
  10. place_pieces
    {"pieces":["half_loop_up","half_loop_down","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":15,"dir":0,"slope":0,"x":34,"y":45,"z":272},"placed_this_call":1,"rejection":{"error":"Twister Roller Coaster 1 in the way","index":1,"piece":"half_loop_down"},"total_placed":52}
  11. valid_next_pieces
    {"cursor":{"bank":15,"dir":0,"slope":0,"x":34,"y":45,"z":272},"valid_pieces":["left_corkscrew_down","right_corkscrew_down"]}
  12. place_pieces
    {"pieces":["right_corkscrew_down","flat_to_down_25","down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_right_bank","banked_right_turn_5","right_bank_to_flat","s_bend_right"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":1,"slope":6,"x":33,"y":50,"z":152},"placed_this_call":4,"rejection":{"error":"Twister Roller Coaster 1 in the way","index":4,"piece":"down_25"},"total_placed":56}
  13. place_piecesrejected
    {"pieces":[]}
    pieces array cannot be empty
  14. undo_piece
    {"cursor":{"bank":0,"dir":1,"slope":6,"x":33,"y":49,"z":168},"pieces_placed":55,"removed":"down_25"}
  15. undo_piece
    {"cursor":{"bank":0,"dir":1,"slope":6,"x":33,"y":48,"z":184},"pieces_placed":54,"removed":"down_25"}
  16. undo_piece
    {"cursor":{"bank":0,"dir":1,"slope":0,"x":33,"y":47,"z":192},"pieces_placed":53,"removed":"flat_to_down_25"}
  17. undo_piecerejected
    undo failed: Track element not found
  18. get_state
    {"circuit_closed":false,"cursor":{"bank":0,"dir":1,"slope":0,"x":33,"y":47,"z":192},"finalized":false,"pieces_placed":53,"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60","down_60_to_down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","half_loop_up","right_corkscre… (1299 chars)
  19. place_pieces
    {"pieces":["flat","flat","flat","flat_to_down_25","right_turn_5_down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":37,"y":53,"z":112},"placed_this_call":6,"total_placed":59}
  20. place_pieces
    {"pieces":["flat_to_up_25","right_vertical_loop","down_25_to_flat","s_bend_right","s_bend_right","flat_to_up_25","right_vertical_loop","down_25_to_flat","s_bend_right","s_bend_right","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","brakes","brakes","flat_to_left_bank","banked_left_turn_3","banked_left_turn_3","left_bank_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":2,"x":48,"y":50,"z":120},"placed_this_call":6,"rejection":{"error":"Twister Roller Coaster 1 in the way","index":6,"piece":"right_vertical_loop"},"total_placed":65}
  21. undo_piece
    {"cursor":{"bank":0,"dir":2,"slope":0,"x":47,"y":50,"z":112},"pieces_placed":64,"removed":"flat_to_up_25"}
  22. place_pieces
    {"pieces":["s_bend_right","s_bend_right","s_bend_right","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","brakes","brakes","brakes","flat_to_left_bank","banked_left_turn_3","banked_left_turn_3","left_bank_to_flat"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"placed_this_call":14,"total_placed":78}

  23. Circuit closed. Testing now.

  24. finish_and_test
    {"bounds":{"max_tile_x":65,"max_tile_y":53,"max_z":408,"min_tile_x":21,"min_tile_y":45,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60","down_60_to_down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","half_loop_up","right_corkscrew_down","flat","flat"… (2256 chars)

  25. Intensity 14.7 tanked it. Rebuilding with gentler geometry (no high-speed s-bends, wider turns, softer pullout).

  26. demolish
    {"demolished":0}
  27. new_ride
    {"dir":0,"ride_type":51,"x":62,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"ride_id":0}
  28. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25","down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":30,"y":50,"z":112},"placed_this_call":32,"total_placed":32}
  29. place_pieces
    {"pieces":["flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":27,"y":45,"z":112},"placed_this_call":12,"total_placed":44}
  30. place_pieces
    {"pieces":["flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","right_vertical_loop","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":47,"y":45,"z":112},"placed_this_call":18,"total_placed":62}
  31. place_pieces
    {"pieces":["flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","brakes","brakes","brakes","brakes","flat","flat","flat","flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"placed_this_call":20,"total_placed":82}
  32. finish_and_test
    {"bounds":{"max_tile_x":66,"max_tile_y":50,"max_z":376,"min_tile_x":21,"min_tile_y":45,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","fla… (2262 chars)

  33. Banked 6.99 at intensity 9.94. One quick refinement — swap dead flat track for an extra airtime hill.

  34. demolish
    {"demolished":0}
  35. new_ride
    {"dir":0,"ride_type":51,"x":62,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"ride_id":0}
  36. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":27,"y":45,"z":112},"placed_this_call":44,"total_placed":44}
  37. place_pieces
    {"pieces":["flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","brakes","brakes","brakes","brakes","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":62,"y":50,"z":112},"placed_this_call":38,"total_placed":82}
  38. finish_and_test
    {"bounds":{"max_tile_x":66,"max_tile_y":50,"max_z":376,"min_tile_x":21,"min_tile_y":45,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","fla… (2305 chars)
  39. best_result
    {"bounds":{"max_tile_x":66,"max_tile_y":50,"max_z":376,"min_tile_x":21,"min_tile_y":45,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","fla… (2262 chars)

  40. Done — I'll stop here with the score banked. **Best coaster this round: "Twister" steel twister at (62,50) — 82 pieces, 15-piece chain lift to a 30 ft-class first drop through a 60° plunge, then 5 inversions (3 vertical loops + a corkscrew turnaround + a mid-course loop) strung between six airtime camelbacks, closing with a wide banked 180 — excitement 6.99 (intensity 9.94, nausea 6.04, 58 air-time, 11 drops, similarity 0.39).** Notes for next round: intensity is the binding constraint (a 14.7 variant with high-speed s-bends scored only 2.16), and max lateral G sits at 2.99 — mostly from the corkscrew taken at full post-drop speed. Slowing that element is the most likely path to buying headroom for more inversions.

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