Patch Con

Patch Con ~ Defend the Library! is a Touhou spinoff fangame in which you must fend off waves of increasingly powerful foes with your own army, which you can expand and upgrade with the points received in battle. If your "base" suffers 20 hits, it's game over. The player also starts with five single-use spell cards that provide status buffs.

The game has four difficulty levels, several extra modes (including Tower Defense), and a large selection of characters to choose from.

According to the token plot, Patchy developed a spell to create golem armies, only to have it stolen by Marisa, whose next targets are Patchy's books. The final wave of enemies is always a squad of giant Marisas.

A translation patch can be found here.

Tropes used in Patch Con include:

Asteroids Monster - The Suika unit splits into two Mini Suika units upon defeat. Mini Suika units split into two Teeny Suika units upon defeat.
Elemental Powers - Your five spell cards are based on the Eastern elements of Fire, Water, Earth, Wood, and Metal.
Endless Game - Endless Mode
Excuse Plot
Game Breaker - Buying tons of a level 1 unit (>100), upgrading it the point where selling just a few pays for the next upgrade (somewhere past 10), then selling them in mass will net you a huge amount of cash. Easiest to do on 100K mode.
Giant Mook - Every few game hours or so, a pair of giant versions of one of the characters will appear. They take lots more punishment than the regular-sized enemies. In Boss Rush mode, all enemies are giants.
Hold the Line - Defend The Library!
Spread Shot - A common upgrade for danmaku types.
Tactical Rock-Paper-Scissors - There are three types of characters: melee, danmaku, and flying. Melee units take enough punishment to close with danmaku, which have long range and tend to take flying units down quickly, which are slow but powerful ranged units that tend to hit in a large area and kill melee units in a couple hits.
Taking You with Me - Meiling and Mokou are both melee units that explode when destroyed.
Tower Defense - There is a mode like this
Zerg Rush - Averted: Yes, it is tempting to fill over half the screen with 1250 level 1 Cirno (the cheapest melee unit) in 100k Mode (and should be tried at least once), but a mob of level 4 Reimu (flight) will kick your ass. Winning with 10 level 10 units is much easier.
- Also, Alice spawns at level 1 with two melee dolls, and gains an additional doll every few levels thereafter. Twenty of those, pumped up by a few levels, gives you eighty respawning melee units as well as twenty fairly powerful gunners.
- You can force this upon yourself by rapidly clicking the button to spawn the next wave of enemies, eventually spawning all of the enemies that would have been spawned over the course of the game all at once.