TapDefense Reviewed Through the Eyes of a Game Designer

Tuesday, December 30th, 2008

As I was stepping on the plane for a holiday visit to San Diego, I went on the Apple App Store on my iPhone and downloaded the free game TapDefense. As a rule I generally do not expect much from free games, especially for the iPhone and just got the game because it was high on the popularity list and to waste some time on my four-hour flight. I was very surprised by how good this unassumingly named game was. The game itself is a tower defense strategy game that is surprisingly deep.

The Premise
Your job is to defend the gates of heaven from 41 waves of invading demon hordes through the strategic placement of a variety of different defensive towers. There are three different difficulty levels in the game and the only difference (and it is an important one) between easy, medium and hard is the path the demons take to the gate. Easy mode’s path is very circuitous and the map provides a number of great choke points to place towers, while medium mode has fewer turns and a more direct path to the gate and hard mode is nearly a direct path. At the start of every level the player may place towers without the threat of the demons. The player may also pause the action in the game at any point and upgrade existing towers or place additional towers.

The Gameplay Mechanics
As I play games I am always analyzing the gameplay mechanics and boiling it down to a few tenants of game design that I believe the developers had in mind when creating the game. The game mechanics are designed to work in a certain way to encourage the player to play in a certain manner. Here are the two game design tenants that I see the game mechanics supporting.

1) The first tenant is that the player must strategically place towers and properly allocate resources.

This means that the player must maximize the effectiveness of each tower he places down. The towers themselves have strengths and weakness that the player must take into account. The game reinforces this tenant by rewarding the player for using the fewest and lowest cost towers to defeat each of the waves.

How TapDefense accomplishes this is through the way the game gives money to the player by using compounding interest after each level is complete. At the end of each level the player receives interest on their remaining gold. The rate is 10% at the start of the game and can be raised to higher rates by spending Halos.

The interest rate game mechanic is an interesting one and certainly has its tradeoffs. The mechanic weights its punishment of mistakes made at the start of the game heavily, making it nearly impossible to recover during the later waves. Perfecting the opening is much more important than the ending. I call this feature out because it is exactly the opposite of what most game difficulty curves are like. In general mistakes at the later levels are punished more gravely than at the beginning.

In the end, I believe that it was a good choice because it furthers the design tenant by rewarding players who scrutinize their tower placement and to win each level with the minimum resources necessary. It also encourages replay value as players attempt to maximize their money totals.

2) The second game design tenant is that the player must utilize a variety of towers.

TapDefense achieves this through the use of the different varieties of demons that the game throws at you each have their vulnerabilities and resistances to different kinds of towers. In order to be successful the player must use a variety of towers.

These game design tenants in TapDefense keep the gameplay interesting and varied. So based off of the design tenants the key to winning is the proper allocation of resources to maximize effectiveness and the use of a variety of towers.

Tower Variety
I will list out the various towers the game has available. TapDefense begins with the player only having access to the Arrow Tower, Bomb Tower and Water Tower. Additional towers are unlocked through the use of Halos, which are earned at predetermined level intervals.

Arrow Tower

These are cheapest towers to place and upgrade. They have good range and have a fast firing rate.

Bomb Tower

These towers are more expensive than the Arrow towers and have a slower firing rate and range, but more than make up for it by doing very good area effect damage.

Water Tower

This tower slows enemy movement and when fully upgrade does decent direct damage.

Storm Tower

These towers have short range, but they take off a percentage of a demon’s life. Storm towers scale incredibly well. While these towers are not useful early on, since most of the enemies do not have a high health total, in later waves when enemies have outrageous hit points these towers become essential to victory.

Ice Tower

This tower slows down entire enemy groups.

Magic Tower

This in my opinion is the most important tower to have during the higher waves. The Magic tower has a high rate of fire, the best range in the game and when fully upgraded do very good area of effect damage.

Earthquake Tower

This tower has decent range and causes very good damage, but it takes up the equivalent space of four towers. The Earthquake Tower is also special in that it is the only tower that requires the player to manually operate it by shaking the iPhone.

Problems I would like to see addressed in the game

1. Occasionally the game will stall and not load

This issue was not just isolated to only my iPhone as my girlfriend’s phone had similar issues with the game.

2. Frame Rate Issues

When there are a lot of demons on the screen and lots of towers shooting at them, the frame rate can drop very significantly. This can hurt the game to the point where the game will not respond to your command to pause.

3. The sell tower button is in the same spot as the pause button

Since the pause button is such an important button (used frequently to assess the situation), the UI choice to place the sell tower button in the same spot with no confirmation leads to some very unhappy accidents. Selling a tower only recoups a small fraction of the cost to build the tower so this is simply unforgivable.

4. No Undo

If you do manage to sell a tower or place a tower down by accident, there is no undo button. Not a killer, but occasionally annoying.

5. Add a level rewind feature

As far as I could tell there was no level save feature, even if they had this feature it would not resolve the issues, because mistakes early in the game ripple throughout the rest of the game. I would suggest the inclusion of a per level rewind feature to go back in time to the spot where the mistake occurred. Currently, in order to atone for mistakes the game must be restarted from the beginning.

TapDefense is an ad-supported game and there are ads after every level played. They are small and out of the way though and really never bothered me. If we can have more high quality games like TapDefense made free through ads, I am all for it.

If you have an iPhone, you should download TapDefense. The gameplay is addictive and provided me with hours of entertainment. It is free so what have you got to lose?

See my other related articles also:
The iPhone 3G & AT&T Service Review
Become a Video Game Designer: Everything You Need to Know Part 1
10 Greatest Video Game Designers Part 1
Low Skill Cap and Luck (RNG) in World of Warcraft PVP
What Video Games Taught Me About Life
Roger Ebert is Right: Games are Not High Art…Yet
What’s Bad About Call of Duty 4: Modern Warfare Multiplayer Mode?
Dead Space Through the Eyes of a Game Designer
Call of Duty: World at War Through the Eyes of a Game Designer
Gears of War 2 Through the Eyes of a Game Designer
Best Games of All Time by Genre Part 1
8 of the Most Underrated or Overlooked Video Games of All Time
Pimps at Sea err I mean Age of Booty & Gen 13 Cosplay
My Student Films 2: EverQuest Documentary and Guilty Gear Isuka Trailer
Top 5 Greatest Moments in Competitive Gaming (eSports)
Best MMA Fights & Genki Sudo: Real Life Video Game Character

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