:root {
    --bg-dark: #121822; /* Very dark blue-gray */
    --bg-panel: #1A2232;
    --text-primary: #E2E8F0;
    --text-secondary: #94A3B8;
    
    --brand-primary: #3B82F6; /* Blue */
    --brand-primary-hover: #2563EB;
    
    --brand-accent: #8B5CF6; /* Purple */
    --brand-accent-hover: #7C3AED;
    
    --color-up: #EF4444; /* Red Spin Up */
    --color-down: #0EA5E9; /* Blue Spin Down */
    --color-coupling-unknown: #475569;
    --color-coupling-pos: #10B981; /* Green + */
    --color-coupling-neg: #EF4444; /* Red - */
    
    --warning: #F59E0B;
    --warning-hover: #D97706;
    
    --gap: 30px;
    --cell-size: 60px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-primary);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden;
}

.app-container {
    width: 100%;
    max-width: 1200px;
    height: 100vh;
    position: relative;
    padding: 2rem;
}

/* Screens */
.screen {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    opacity: 0;
    transition: opacity 0.4s ease;
}

.screen.active {
    display: flex;
    opacity: 1;
}

/* Typography */
h1.dynamic-title {
    font-size: 4.5rem;
    font-weight: 800;
    margin-bottom: 3rem;
    background: linear-gradient(to right, var(--brand-primary), var(--brand-accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0px 4px 20px rgba(139, 92, 246, 0.2);
}

h2 {
    font-size: 2.5rem;
    font-weight: 600;
    margin-bottom: 2rem;
}

/* Buttons */
.btn {
    font-family: 'Inter', sans-serif;
    font-size: 1.2rem;
    font-weight: 600;
    padding: 1rem 2rem;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    transition: transform 0.2s, background-color 0.3s, box-shadow 0.3s;
    color: #fff;
    width: 100%;
    max-width: 300px;
    margin-bottom: 1rem;
}

.btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.btn:active:not(:disabled) {
    transform: translateY(0px);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary { background-color: var(--brand-primary); }
.btn-primary:hover { background-color: var(--brand-primary-hover); }

.btn-secondary { background-color: transparent; border: 2px solid var(--text-secondary); color: var(--text-primary); }
.btn-secondary:hover { background-color: var(--text-secondary); color: #fff; }

.btn-accent { background-color: var(--brand-accent); }
.btn-accent:hover { background-color: var(--brand-accent-hover); }

.btn-warning { background-color: var(--warning); }
.btn-warning:hover { background-color: var(--warning-hover); }

.btn-success { background-color: var(--color-coupling-pos); }

.btn-back { width: auto; max-width: 200px; padding: 0.8rem 1.5rem; background-color: var(--bg-panel); color: var(--text-primary); margin-top: 1rem; }

.top-nav {
    width: 100%;
    display: flex;
    justify-content: flex-start;
    padding: 1rem 0;
    position: absolute;
    top: 0;
    left: 2rem;
}

.menu-buttons {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    width: 100%;
}

/* Tutorial Layout */
.tutorial-layout {
    justify-content: center;
    align-items: flex-start;
    max-width: 800px;
    margin: auto;
}

.tutorial-content {
    background: var(--bg-panel);
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    width: 100%;
}
.tutorial-content h3 { margin-top: 1.5rem; margin-bottom: 0.5rem;}
.tutorial-content ul, .tutorial-content ol { margin-left: 2rem; line-height: 1.8; color: var(--text-secondary); font-size: 1.1rem; }
.tutorial-content li { margin-bottom: 0.5rem; }

.text-green { color: var(--color-coupling-pos); font-weight: bold; }
.text-red { color: var(--color-coupling-neg); font-weight: bold; }

/* Game Layout */
.game-layout {
    flex-direction: row;
    align-items: stretch;
    justify-content: space-between;
    padding-top: 6rem;
}

.game-body {
    display: flex;
    width: 100%;
    gap: 2rem;
    height: 100%;
}

.history-panel {
    flex: 1;
    background: var(--bg-panel);
    border-radius: 16px;
    padding: 2rem;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 2rem;
    /* Custom Scrollbar */
}
.history-panel::-webkit-scrollbar { width: 8px; }
.history-panel::-webkit-scrollbar-track { background: var(--bg-dark); border-radius: 8px; }
.history-panel::-webkit-scrollbar-thumb { background: var(--text-secondary); border-radius: 8px; }

.control-panel {
    width: 350px;
    background: var(--bg-panel);
    border-radius: 16px;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    box-shadow: -5px 0 20px rgba(0,0,0,0.2);
}

.panel-title {
    margin-bottom: 1rem;
    color: var(--brand-primary);
}

.status-text {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 2rem;
    color: var(--text-primary);
}

.panel-actions {
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    align-items: center;
}

.divider {
    width: 100%;
    border: none;
    height: 2px;
    background: var(--bg-dark);
    margin: 1.5rem 0;
}

.pulse {
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% { transform: scale(1); box-shadow: 0 0 0 0 rgba(139, 92, 246, 0.4); }
    70% { transform: scale(1.02); box-shadow: 0 0 0 10px rgba(139, 92, 246, 0); }
    100% { transform: scale(1); box-shadow: 0 0 0 0 rgba(139, 92, 246, 0); }
}

/* Spin Grid Layout */
.grid-row-container {
    display: flex;
    align-items: center;
    gap: 3rem;
    background: rgba(0,0,0,0.2);
    padding: 2rem;
    border-radius: 12px;
}

.grid-container {
    position: relative;
    /* Grid populated via JS */
}

/* Arrow Component */
.arrow {
    position: absolute;
    width: calc(var(--cell-size) * 0.4);
    height: calc(var(--cell-size) * 0.8);
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    cursor: pointer;
    clip-path: polygon(50% 0%, 100% 30%, 65% 30%, 65% 100%, 35% 100%, 35% 30%, 0% 30%);
}

.arrow.up {
    background-color: var(--color-up);
    transform: translate(-50%, -50%) rotate(0deg);
}

.arrow.down {
    background-color: var(--color-down);
    transform: translate(-50%, -50%) rotate(180deg);
}

.arrow:hover {
    filter: brightness(1.2);
    /* Tiny scale up on top of transform not easily possible when transform also has rotate, 
       handled via brightness instead */
}

/* Coupling Component */
.coupling {
    position: absolute;
    width: calc(var(--gap) * 0.8);
    height: calc(var(--gap) * 0.8);
    background-color: var(--color-coupling-unknown);
    transform: translate(-50%, -50%);
    border-radius: 4px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    font-weight: bold;
    color: white;
    cursor: default;
    transition: background-color 0.3s, transform 0.2s;
    user-select: none;
}

.coupling[data-val="1"] {
    background-color: var(--color-coupling-pos);
}

.coupling[data-val="0"] {
    background-color: var(--color-coupling-neg);
}

/* Interaction modes */
.mode-couplings .coupling {
    cursor: pointer;
}
.mode-couplings .coupling:hover {
    transform: translate(-50%, -50%) scale(1.1);
}
.mode-couplings .arrow {
    cursor: default;
    opacity: 0.7;
}

.energy-label {
    font-size: 2rem;
    font-weight: bold;
    color: var(--warning);
}

/* Modals */
.modal {
    display: none; 
    position: fixed; 
    z-index: 100; left: 0; top: 0; width: 100%; height: 100%;
    background-color: rgba(0,0,0,0.8);
    backdrop-filter: blur(5px);
    justify-content: center;
    align-items: center;
    opacity: 0;
    transition: opacity 0.3s;
}
.modal.show {
    display: flex;
    opacity: 1;
}
.modal-content {
    background-color: var(--bg-panel);
    padding: 3rem;
    border-radius: 16px;
    text-align: center;
    box-shadow: 0 15px 50px rgba(0,0,0,0.5);
    max-width: 600px;
}
.modal-content.locked-grid {
    margin-top: 2rem;
    padding: 1rem;
    background: rgba(0,0,0,0.2);
}
.mt-4 { margin-top: 2rem; }

#fireworks-canvas {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    pointer-events: none;
    z-index: 999;
}