We need a bit more information to help you with this issue. Please share your system specifications in the following format:
Please share the Besiege log file:
Your log file can be found under the Besiege game folder in “Besiege_Data/output_log.txt” So if your Steam is installed in the default location, it would be at: “C:\Program Files (x86)\Steam\steamapps\common\Besiege\Besiege_Data\output_log.txt”
On Mac the log file should be located at: “~/Library/Logs/Unity/Player.log”.
On linux it can be found in ~/.config/unity3d/Spiderling Games/Besiege/Player.log
Once you've found your log file, please upload it to https://pastebin.com/ and share the URL of the uploaded file.
In some cases we need your software list to determine if some specific software may be interfering with the game.
Here's a step by step tutorial on how to gather the DxDiag information: http://steamcommunity.com/app/233250/discussions/2/648814845450819657/ Please share the uploaded DxDiag report.