fix stacking issues for irregular structures
new structures, refactor

still need to fix stacking issues when multiple structures are in the same
x range
fix stacking, add scrolling
HUD tweaks, fix bullet render
slight distract delay
fix timing issues, add pause

also auto-pause when focus leaves window
some rendering tweaks, binocular mode on game over

also auto pause/resume when window loses/gains focus
auto show/hide cursor