Thanks for playing! Appreciate you giving it a shot even with the lack of tiles.
The shop is only accessible between waves, so when the "next wave timer" is ticking, you can pause to access it. The pause button is different depending on if you're playing the web browser build (Backspace) or the desktop build (Escape).
Escape feels like a more natural pause button, BUT when you hit the button on web it can affect things like full screen and mouse mode, so I decided to make backspace a substitute on web.
Once you pause you'll be able to click on whichever items you want to buy (If you have enough gold for it).
Once you buy some tiles, you can un-pause, and place them in any grid cells that are empty. You'll know you can place a tile by it's preview mesh (Just a white dither silhouette). Left click to place down a tile:
