Good job on your entry, i'll give you some tips to improve some aspects of the game.
A fast respawn is good, but there is problems if its too fast, the player will mostly always be moving when he dies, after all, his last intention was probably to dodge an incoming death. So if you respawn him instantaneously and let him have control over his character immediately, he will still be inputing some buttons to do an action he doesnt want to do anymore. In the case of your game, sometimes when you die from a spike you'll respawn and immediately run on it one or two more times. You get punished for a mistake you didin't make and it's a bit unfair.
The spike on the ground is a good attack but also, if it's instantaneous you can't really dodge it when it spawns in front of you, at the end i was just standing still when the spike was not on the ground to wait for it to show up so i could cross the arena "safely". You probably want to put the spike on a small delay with a visual indication of his spawning location or at least make it so it only spawn far enough for the player to react.