Glissaria

Glissaria is an online 2D Flash part-RPG, part-Tower Defense, and part-Match Three game developed by Arkeus originally for Ludum Dare 21.

You play as Prince Trey, who has been sent by his father, King Varon, to bolster the defenses of the northern parts of his kingdom due to the influx of monster attacks all across the kingdom.

The gameplay is fairly simple. You swap and match at least five tiles of the same type to obtain resources. These resources can be used to build (wood) and upgrade towers (iron, adamantite, mythril), gain experience and heal the Prince (red stars), obtain various pieces of equipment to equip for the Prince (chests), or gain powerful gems and treasure to bolster the strength and abilities of the towers (gold orbs). Monsters will march along the path to the castle, and while Prince Trey will move to attack them as they approach, you must strategically place and upgrade your towers to provide backup and take out monsters as optimally as possible. Will you be able to keep up and repel the monsters on eight different maps?

This game can be found at here.

Tropes used in Glissaria include:

Crutch Character: Peon Towers. They are good at fending off early waves of enemies (in fairly large groups) and are cheap to deploy. However, in the mid to late waves, they begin to fall behind compared to the other types of towers due to having the weakest upgrade path - not to mention having the slowest firing speed and a low range.
Death Is a Slap on The Wrist: For Prince Trey it is. After getting killed by monsters, it only takes a few seconds for him to respawn with full health and no penalties. Which makes it less useful to match red star tiles to heal him, other than for clearing up the tile board.
Elemental Crafting: In terms of the strength of equipment materials (in general) from lowest to greatest: wood < iron < steel < adamantite < mythril < sunsteel < seastone < banelight. This gets Subverted a bit when you take into account the unique stat-bonuses that each piece of equipment gives. Some equipment from lower-strength materials could provide better bonuses than those of a higher-strength material. However, it gets played straight again with the tower upgrades (wood < iron < adamantite < mythril).
Endless Game: The aptly titled, "Endless Mode", which allows to play on one of eight maps available until your castle falls.
Excuse Plot: The only mention of the story (described in the above description) is in the beginning of the first stage. Afterwards, it is completely ignored.
Fragile Speedster: Swift Towers. While they aren't as powerful as most of the other towers (excluding Sweep Towers) in terms of raw damage, they can fire three projectiles per second - making them great for concentrated damage.
Match Five Game: The tile-board matching portion of the game.
Mighty Glacier: Skybound Towers. They can only fire one projectile every 1.2 seconds but, their attack power is the highest out of all towers (exemplified when upgraded) and has the greatest range.