OTTTD

OTTTD download

It is a tower defense game that pits you against weird creatures.
Download from the developer's website

Alternative apps

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Build cannons, save money, destroy the enemy with the help of secret weaponry.
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Destroy epic bosses and fight hordes of enemies that plan to kill you.
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Help friendly towns to grow and glow by building neighborhoods.
WidgetTD
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Innovative action-strategy game for Mac.
Defender's Quest: Valley of the Forgotten
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This is a fun, fast-paced Tower Defense and RPG game.