The IS-LM model holds the price level fixed and asks a short-run question: what pair of output (Y) and interest rate (r) makes both the goods market and the money market clear at once?
The IS curve is every (Y, r) where planned spending equals output. It slopes down: a lower interest rate makes investment cheaper, so firms spend more and output is higher. More government spending shifts the whole curve outward.
The LM curve is every (Y, r) where money demand equals a fixed money supply. It slopes up: higher income means people want more money, which — with the supply fixed — pushes the interest rate up. Printing more money shifts the curve outward, lowering r at every Y.
Only the crossing satisfies both. Fiscal expansion pushes output up but drags the interest rate up with it — crowding out private investment. Monetary expansion lifts output while pushing the interest rate down. Same goal, opposite price: that trade-off is the whole point of the crosshair.
Something in the simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.