{
  "analysis": "The output is 268858 bytes, way over the 69000 byte budget. I need to use more efficient cursor movements - specifically using `\\n` (1 byte) instead of `ESC[nB` (4-6 bytes) for moving down when at column 1, and `\\b` (1 byte) instead of `ESC[nD` for small left movements.",
  "plan": "Redesign the encoder to use `\\n`, `\\r`, and `\\b` more efficiently for cursor movement.",
  "commands": [
    {
      "keystrokes": "cat > /app/termzip_ansi.py << 'EOF'\nimport struct\nimport sys\n\ndef find_runs(changes):\n    \"\"\"Find contiguous runs of changed columns.\"\"\"\n    runs = []\n    if not changes:\n        return runs\n    run_start = changes[0]\n    run_end = changes[0]\n    for c in changes[1:]:\n        if c == run_end + 1:\n            run_end = c\n        else:\n            runs.append((run_start, run_end))\n            run_start = run_end = c\n    runs.append((run_start, run_end))\n    return runs\n\ndef encode_move(out, from_r, from_c, to_r, to_c):\n    \"\"\"Encode cursor movement from (from_r, from_c) to (to_r, to_c).\"\"\"\n    if from_r == to_r and from_c == to_c:\n        return\n    if from_r == to_r:\n        # Same row: use CUF or CUB (or backspace for small moves)\n        dc = to_c - from_c\n        if dc == 1:\n            out.append(' ')  # Space and backspace is 2 bytes, same as ESC[1C\n            out.append('\\b')\n        elif dc > 0:\n            out.append(f'\\x1b[{dc}C')\n        elif dc == -1:\n            out.append('\\b')\n        elif dc >= -3:\n            out.append('\\b' * (-dc))\n        else:\n            out.append(f'\\x1b[{-dc}D')\n    else:\n        # Different rows\n        if from_c == 1 and to_c == 1:\n            # At col 1, going to col 1: use newlines\n            dr = to_r - from_r\n            if dr > 0:\n                out.append('\\n' * dr)\n            else:\n                out.append('\\x1b[' + str(-dr) + 'A')\n        else:\n            # CR + vertical + horizontal\n            out.append('\\r')\n            dr = to_r - from_r\n            if dr > 0:\n                out.append('\\n' * dr)\n            elif dr < 0:\n                out.append(f'\\x1b[{-dr}A')\n            if to_c > 1:\n                out.append(f'\\x1b[{to_c-1}C')\n\ndef main():\n    if len(sys.argv) != 2:\n        sys.exit(1)\n    \n    with open(sys.argv[1], 'rb') as f:\n        magic = f.read(4)\n        if magic != b'TZA1':\n            sys.exit(1)\n        w, h = struct.unpack('<HH', f.read(4))\n        n_frames, max_bytes = struct.unpack('<II', f.read(8))\n        \n        # Read all frames\n        frames = [f.read(w * h) for _ in range(n_frames)]\n    \n    out = []\n    cursor_r, cursor_c = 1, 1\n    \n    # Frame 0: write non-space characters\n    for r in range(h):\n        row = frames[0][r*w:(r+1)*w]\n        non_space = [c for c in range(w) if row[c] != 32]\n        runs = find_runs(non_space)\n        for start, end in runs:\n            encode_move(out, cursor_r, cursor_c, r+1, start+1)\n            out.append(row[start:end+1].decode('latin1'))\n            cursor_r, cursor_c = r+1, end+2\n    out.append('\\x1e')\n    \n    # Subsequent frames\n    for i in range(1, n_frames):\n        # Find changed rows\n        changed_rows = [r for r in range(h) if frames[i-1][r*w:(r+1)*w] != frames[i][r*w:(r+1)*w]]\n        \n        if not changed_rows:\n            out.append('\\x1e')\n            continue\n        \n        for r in changed_rows:\n            prev_row = frames[i-1][r*w:(r+1)*w]\n            curr_row = frames[i][r*w:(r+1)*w]\n            changes = [c for c in range(w) if prev_row[c] != curr_row[c]]\n            runs = find_runs(changes)\n            \n            # Calculate cost of EL + rewrite\n            cost_erase = 1  # CR\n            dr = r - (cursor_r - 1)\n            if dr > 0:\n                cost_erase += dr  # \\n * dr\n            elif dr < 0:\n                cost_erase += 4 + len(str(-dr))  # ESC[nA\n            cost_erase += 4 + w  # ESC[2K + row content\n            \n            # Calculate cost of partial updates\n            cost_partial = 0\n            temp_r, temp_c = cursor_r, cursor_c\n            for start, end in runs:\n                if temp_r == r+1:\n                    dc = (start+1) - temp_c\n                    if dc > 0:\n                        cost_partial += 4 + len(str(dc))\n                    elif dc < 0:\n                        cost_partial += min(-dc, 4 + len(str(-dc)))\n                else:\n                    cost_partial += 1  # CR\n                    dr = r - (temp_r - 1)\n                    if dr > 0:\n                        cost_partial += dr  # \\n * dr\n                    elif dr < 0:\n                        cost_partial += 4 + len(str(-dr))\n                    if start+1 > 1:\n                        cost_partial += 4 + len(str(start))\n                temp_r, temp_c = r+1, end+2\n            cost_partial += len(changes)\n            \n            # Choose cheaper\n            if cost_erase <= cost_partial:\n                encode_move(out, cursor_r, cursor_c, r+1, 1)\n                out.append('\\x1b[2K')\n                out.append(curr_row.decode('latin1'))\n                cursor_r, cursor_c = r+1, w+1\n            else:\n                for start, end in runs:\n                    encode_move(out, cursor_r, cursor_c, r+1, start+1)\n                    out.append(curr_row[start:end+1].decode('latin1'))\n                    cursor_r, cursor_c = r+1, end+2\n        \n        out.append('\\x1e')\n    \n    sys.stdout.write(''.join(out))\n\nif __name__ == '__main__':\n    main()\nEOF\n",
      "duration": 0.5
    }
  ]
}