The explanation of starting positions is awkward, possibly there should be a 'placing' between "by" and "their mechs"? I like that melee uses the same mechanics as shooting, but rolls 2d10 keep 1 to give it an advantage on damage and success, it's a nice simple way to make melee decent without a ton of additional rules. The section on reactions is also worded awkwardly.
This is a nice and simple game of mech combat, with an interesting idea in the heat mechanics. It doesn't quite line up with the jam theme, given that the heat actions are not substantially more powerful than the cool actions, but the differing choices based on your mech's current heat is a neat one. Beyond the heat thing, which is a staple of mech games, it doesn't to much that novel, but is a nice tightly designed little game.