Tier
Upgrade
Prerequisites
City Cash cost
Time (minutes)
XP for researching
1
Bigger Stacks
City Level 5
500
15
35
2
White Hot Spikes
City Level 8
1,200
90
70
3
Spiked Ball Factory
City Level 12
7,500
2,160
500
4
Spiked Mines
City Level 20, High Explosives Workshop built
50,000
5,760
1,000
1
Faster Production
—
500
30
60
2
Even Faster Production
City Level 8
2,000
120
100
3
MOAB-SHREDR Spikes
City Level 15, Anti MOAB Research Lab built
20,000
2,160
225
4
Spike Storm
City Level 20, Spike Dispersal Unit built
36,000
4,320
1,000
Tier
Upgrade
Prerequisites
City Cash cost
Bloonstone cost
Time (minutes)
XP for researching
1
Faster Shooting
—
200
—
5
25
2
Even Faster Shooting
City Level 4
1,000
—
90
60
3
Tack Sprayer
City Level 10
6,000
20
1,440
350
4
Ring of Fire
City Level 18, Thermite Plant built
10,500
50
1,440
700
1
Extra Range Tacks
—
240
—
15
25
2
Super Range Tacks
City Level 5
1,200
—
60
50
3
Blade Shooter
City Level 10
5,200
20
960
100
4
Blade Maelstrom
City Level 20, Blademill built
26,000
50
2,880
800
Tier
Upgrade
Prerequisites
City Cash cost
Bloonstone cost
Time (minutes)
XP for researching
1
Bigger Stacks
City Level 5
500
—
15
35
2
White Hot Spikes
City Level 8
1,200
—
90
70
3
Spiked Ball Factory
City Level 12
7,500
20
2,160
500
4
Spiked Mines
City Level 20, High Explosives Workshop built
50,000
50
5,760
1,000
1
Faster Production
—
500
—
30
60
2
Even Faster Production
City Level 8
2,000
—
120
100
3
MOAB-SHREDR Spikes
City Level 15, Anti MOAB Research Lab built
20,000
20
2,160
225
4
Spike Storm
City Level 20, Spike Dispersal Unit built
36,000
50
4,320
1,000
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This article or section needs more images . The editor who added this notice elaborates: building sprites