Thanks for playing! The shop isn't implemented yet, I should probably just remove the button for now. Leveling up requires you to have enough runes for the level to purchase after every level ends, did nothing happen when you pressed the level up button regardless? The portal not showing up after killing everything is definitely not intended, I will look into it.
The weapon switch delay is intended, however I will change it to be less annoying - so you can always start switching but it takes some time to do it instead.