This is likely the best game I've played on Itch.io. I hope you continue to polish it and hopefully release on Steam so people like me can throw more money at you.
Couple things, whenever I place a shielded wall... the game crashes. You can cheat/exploit by placing conveyor belt or conduit on lava to cross it with your mech. Why no large shielded wall... other than my inability to place them without the game exploding... seems logical for that last slot on the menu. Lags a bit when there is a lot on the screen.