Glitches crawl along a winding causeway toward your Crystal Core. Build towers on the glowing pads, upgrade each one down one of two paths, and spend shards between runs on research that takes you to higher waves.
👆 Tap a pad to build · tap a tower to upgrade · tap a glitch to spotlight it ← All gamesCitadel is a free 3D tower defense game you can play in your browser on a phone or a computer, with one finger and no download. Geometric glitches pour out of a rift and crawl along a winding causeway toward the Crystal Core at the near end of the board. You hold them off by building towers on glowing pads beside the causeway and upgrading them as the waves grow. The waves never stop, so the question is always how far you can get, and your run is saved automatically if you close the tab.
Tap an empty pad to open the build menu, then tap a tower to place it. Tap a tower you own to upgrade it, change what it aims at, or sell it; a tower sold in the wave you built it refunds every coin. Each purged glitch pays gold, and every wave you clear pays a bonus. Tap any glitch to put it in the spotlight: every tower in range focuses it and it pays double gold, which is how good players pull ahead. When a wave has finished arriving you can call the next one early for extra gold. Two abilities help in a pinch: Nova blasts the spotlit glitch or the thickest cluster, and Stasis freezes the field for a few seconds. Glitches that reach the Core cost it integrity; when it runs out, the run is over. Chill, Normal and Hard change how much the Core can take and how tough the glitches are, and the speed button runs the game at double speed, or triple after your first boss.
Every tower has three levels, then a choice between two specializations, then a mastery that sharpens the path you picked. New towers unlock one wave before the glitch they answer arrives.
Every run ends with shards: one or more for each wave you cleared, five for each boss and a one-time bonus the first time you reach waves ten, twenty and beyond. Spend them in the research lab on three tabs. Tower labs raise each tower's damage and cut its cost; the economy tab adds starting gold, bounty, interest and better refunds; the core tab adds integrity, repairs after perfect waves and stronger abilities. Reach wave fifteen once and every tower is available from the first wave, and checkpoints let a new run start at wave eleven, twenty-one and later with gold to match. Every five waves you also pick one of three boons for the current run.
Reach wave fifty and the dark dais beside the Core wakes up: for 30,000 gold you can build the Bastion, the Citadel's great cannon. It fires a heavy slug at the strongest glitch on the board every six seconds, at any range, and it grows down a skill tree of very expensive upgrades. Sniper Mode lets you aim it yourself: tap Snipe, the world slows down, then tap any glitch for one enormous shot that ignores armor and shields, made for the Colossus, followed by a long recharge. Siege turns the slugs into explosives that clear crowds and fire faster, and Bulwark makes every tower stronger, knocks glitches back down the causeway and blocks the first leak of each wave. You get one Bastion per run and no run can afford every skill, so the order you buy them in is the decision.
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