At the top of the screen are some buttons that pertain to the game as a whole as opposed to specific actions. These may have different behaviors between a long tap or just a tap.
This icon opens the menu. While the menu is open, the game is paused. From here, you may save the game, exit (with or without saving), load a checkpoint, view the in game help, or jump to your player items (boosts). In the future, customizable settings will be accessed from here.
Tap this icon to open up the player boost screen. It will flash if you have not extended your streak yet for that day. Your current streak, amount of gold coins, and a button to view a reward ad for more gold coins should always be visible up top. View an ad once per day to extend the streak and get a once daily bonus. In the scrollable section, there will be an inventory of items you currently own on top, followed by items you may purchase for gold coins. Tap the icons to get a description of each boost item.
Tap this icon to open the achievements screen. This icon flashes if you have unclaimed rewards. Any time you see a ... you may tap it to expand the text for more details. A list of achievements completed and within your grasp will be shown. Any claimed item rewards will go into the keep. The pending achievements will give a brief description of what to do, how to do it, and what you will receive upon completion.
Tap this icon to keep the camera focused on whatever is currently selected. This is a toggle. This is useful if you want to find the currently selected villager/warrior, etc. Please note that the camera is literally frozen in relation to the object. You cannot move nor zoom.
Long tap this icon to center the camera on the center tile of the map, which is presumably where your keep is: (0,0)
Tap the bell icon to make all your villagers hide by garrisoning in buildings. They will prefer to go into buildings that can attack. Tap it again to have them all leave. Bug: Sometimes they don't all leave. I have not figured out a good differentiator for when you manually tell units to garrison and when the bell does. Some of my prior assumptions are not always true.
Long tap the bell icon to make all villagers and warriors to garrison in buildings.
When something is selected, tap this icon to view more details and customize the selection as needed. From here, you will be able to see all held items, manipulate the actions, see any leveling requirements, control how the general interactions with the world go, etc. Therefore, depending on what is selected, completely different screens will show. In the case of the market, a specialized screen will show to allow trading of gold coins and items. This button does nothing if nothing is selected.
Tap this to open the in game help screens. This will pause the game. It is a more interactive but less detailed version of what is available on this site.
Long tap this to open hints. Towards the top of the screen, hints based on your current selections and actions will cycle every few seconds.
Tap this icon to view all the pending actions. A scrollable view with all your villagers will be up top, and a scrollable view with all your actions will be on bottom You may remove or re-order your pending actions. Additionally, you may selectively assign pending actions to a villager. Tap the red box to select a unit, making it green. You may toggle between adding that action to the selected villagers queue, or replacing all of their actions with the selected action by tapping the Add/Replace button. What is shown is the current status. Then click the arrow to add that action. If you notice the villagers do not seem to be doing any actions, you may try tapping the Clear Actions button, as that will hard reset the action system.
Villagers/Plots/Items: This will show what you are currently selecting, and will correspond with the icons in the upper right.
The time: Tap the time to cycle back and forth between how long you have been playing the game and the attack timer. The attack timer either records how long it has been since the last attack ended or how long the current attack has been going on. If your hero dies, it will count down the time it takes for your hero to respawn.