* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    scroll-behavior: smooth;
}

body {
    min-height: 100vh;
    background: #0b0c10;
    display: flex;
    flex-direction: column;
    color: #e5e7eb;
}

.navbar {
    background: #0b0c10;
    padding: 15px 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: none;
    border-bottom: 1px solid #1f2937;
}

.navbar a {
    color: #93c5fd;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    padding: 8px 16px;
    border-radius: 8px;
}

.navbar a:hover {
    background: rgba(59, 130, 246, 0.15);
    color: #ffffff;
}

.main-content {
    flex: 1;
    padding: 40px 20px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.container {
    width: 100%;
}

h1 {
    text-align: center;
    color: #f3f4f6;
    margin-bottom: 40px;
    font-size: 2.2em;
}

.data-plans {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    margin-bottom: 30px;
}

.plan {
    background: #111827;
    padding: 25px;
    border-radius: 12px;
    border: 1px solid #1f2937;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.plan::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: linear-gradient(to bottom, #3b82f6, #1d4ed8);
    border-radius: 4px 0 0 4px;
}

.plan:hover {
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.12);
    border-color: #3b82f6;
}

.plan-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid #1f2937;
}

.plan-title {
    font-size: 1.2em;
    color: #e5e7eb;
    font-weight: 600;
}

.remove-plan {
    background: #ff4757;
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 6px;
    cursor: pointer;
    display: none;
    transition: all 0.3s ease;
    font-size: 0.9em;
}

.remove-plan:hover {
    background: #ff6b81;
}

.plan:not(:first-child):not(:nth-child(2)) .remove-plan {
    display: block;
}

.input-group {
    display: flex;
    gap: 20px;
}

.input-wrapper {
    flex: 1;
}

label {
    display: block;
    margin-bottom: 8px;
    color: #9ca3af;
    font-weight: 500;
    font-size: 0.95em;
}

input {
    width: 100%;
    padding: 12px;
    border: 2px solid #374151;
    border-radius: 8px;
    font-size: 1em;
    transition: all 0.3s;
    background: #0f172a;
    color: #e5e7eb;
}

input:focus {
    outline: none;
    border-color: #3b82f6;
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.input-wrapper select {
    width: 100%;
    padding: 12px;
    border: 2px solid #374151;
    border-radius: 8px;
    font-size: 1em;
    transition: all 0.3s;
    background: #0f172a;
    color: #e5e7eb;
}
.input-wrapper select:focus {
    outline: none;
    border-color: #3b82f6;
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin: 30px 0;
}

button {
    padding: 14px 28px;
    border: none;
    border-radius: 8px;
    font-size: 1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

#addPlan {
    background: #2ecc71;
    color: white;
}

#addPlan:hover {
    background: #27ae60;
}

#compare {
    background: #3b82f6;
    color: white;
}

#compare:hover {
    background: #2563eb;
}

.result {
    background: #0f172a;
    padding: 25px;
    border-radius: 12px;
    display: none;
    margin-top: 30px;
    border: 1px solid #1f2937;
}

.result.show {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result h2 {
    color: #f3f4f6;
    margin-bottom: 20px;
    font-size: 1.4em;
}

.result p {
    color: #cbd5e1;
    line-height: 1.6;
    margin-bottom: 12px;
    padding: 8px 0;
    border-bottom: 1px solid #1f2937;
}

.best-value {
    color: #34d399;
    font-weight: 600;
    background: rgba(16, 185, 129, 0.1);
    padding: 15px;
    border-radius: 8px;
    margin-top: 15px;
}

.how-to-use {
    background: #0b0c10;
    padding: 40px 20px;
    margin-top: 60px;
    border-top: 1px solid #1f2937;
}

.how-to-use h2 {
    text-align: center;
    color: #f3f4f6;
    margin-bottom: 30px;
    font-size: 1.8em;
    position: relative;
    padding-bottom: 15px;
}

.how-to-use h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, #3b82f6, #1d4ed8);
    border-radius: 2px;
}

.steps-container {
    max-width: 800px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.step {
    text-align: center;
    padding: 20px;
    background: #111827;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
    position: relative;
}

.step-number {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, #3b82f6, #1d4ed8);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    margin: 0 auto 15px;
}

.step h3 {
    color: #e5e7eb;
    margin-bottom: 10px;
    font-size: 1.2em;
}

.step p {
    color: #9ca3af;
    font-size: 0.95em;
    line-height: 1.5;
}

footer {
    background: #0b0c10;
    border-top: 1px solid #1f2937;
    padding: 30px 20px;
    text-align: center;
    margin-top: 0;
}

footer p {
    color: rgba(255, 255, 255, 0.85);
    margin-bottom: 15px;
    font-style: italic;
}

footer a {
    color: #93c5fd;
    text-decoration: none;
    padding: 8px 20px;
    border: 2px solid #3b82f6;
    border-radius: 8px;
    transition: all 0.3s;
    display: inline-block;
}

footer a:hover {
    background: #3b82f6;
    color: #0b0c10;
}

.max-plans-message, .invalid-plans-message {
    color: #f87171;
    text-align: center;
    margin-top: 10px;
    font-weight: 600;
    display: none;
}

@media (max-width: 768px) {
    .main-content {
        padding: 20px 15px;
    }

    .data-plans {
        display: flex;
        flex-direction: column;
        gap: 15px;
    }

    .plan {
        padding: 20px;
        margin-bottom: 15px;
        width: 100%;
        display: block;
    }

    /* Force each plan to take full width */
    .plan:nth-child(n) {
        grid-column: 1 / -1;
    }

    .plan::before {
        width: 100%;
        height: 4px;
        top: 0;
        left: 0;
        background: linear-gradient(to right, #3b82f6, #1d4ed8);
        border-radius: 4px 4px 0 0;
    }

    .input-group {
        flex-direction: column;
        gap: 15px;
    }

    .input-wrapper {
        width: 100%;
    }

    input {
        padding: 14px;
        font-size: 16px;
    }

    .buttons {
        flex-direction: column;
        gap: 12px;
        margin-top: 25px;
    }

    button {
        width: 100%;
        padding: 16px;
        font-size: 1em;
    }

    h1 {
        font-size: 1.6em;
        margin-bottom: 25px;
    }

    .result {
        padding: 20px;
        margin-top: 20px;
    }

    .result h2 {
        font-size: 1.3em;
    }

    .result p {
        font-size: 0.9em;
    }

    .best-value {
        padding: 12px;
        font-size: 0.95em;
    }

    .steps-container {
        grid-template-columns: 1fr;
        gap: 20px;
        padding: 0 10px;
    }

    .step {
        padding: 20px 15px;
        display: flex;
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: 15px;
    }

    .step-number {
        margin: 0 0 5px 0;
    }

    .step h3 {
        width: 100%;
        text-align: center;
        margin-bottom: 8px;
    }

    .step p {
        width: 100%;
        text-align: center;
        font-size: 0.95em;
        line-height: 1.5;
    }

    .how-to-use {
        padding: 30px 15px;
        margin-top: 40px;
    }

    .how-to-use h2 {
        font-size: 1.5em;
        margin-bottom: 25px;
    }

    .navbar {
        padding: 12px 15px;
    }

    .navbar a {
        font-size: 0.9em;
        padding: 8px 12px;
    }

    footer {
        padding: 25px 15px;
    }

    footer p {
        font-size: 0.9em;
        margin-bottom: 15px;
        color: rgba(255, 255, 255, 0.85);
    }

    footer a {
        width: 100%;
        display: block;
        padding: 12px;
        border-color: #3b82f6;
        font-weight: 600;
    }

    footer a:hover {
        background: #3b82f6;
        color: #0b0c10;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    .steps-container {
        grid-template-columns: repeat(3, 1fr);
        gap: 20px;
    }

    .step {
        padding: 20px 15px;
    }
}